Harrison Instruments
Model 151 Theremin User Manual
(Online Version for Instruments with Right-Side Pitch)

Table of Contents




Safety Notices


Unpacking and Inspection


Additional Materials Required


Introduction to the Theremin


Model 151 Theremin Controls and Output Jack


Battery Installation


Setting Up the Model 151 Theremin


Playing the Model 151 Theremin


Grounding and Portable Operation


Tone Control


Model 151 Theremin Specifications


Troubleshooting Guide


Warranty and Repair Service


Contacting Harrison Instruments

1. Safety Notices <back to contents>

Read all the instructions in this manual prior to using this product. Retain these operating instructions for future reference.

When this product is connected to an external device such as an amplifier, a shock hazard may be present.
To avoid electric shock, do not operate this product in the rain or near water.
Do not allow this product to become wet.
Do not replace or supplement this product's battery with an external power supply.
Do not place cables connected to this product in areas where they can cause a trip hazard.
Do not play this instrument at a high volume, especially when using headphones.
Hearing experts advise against the continuous, extended use of headphones.
Do not disassemble this instrument. There are no user serviceable parts inside.
Refer servicing to qualified service personnel.

2. Unpacking and Inspection <back to contents>

The following items are contained in the carton:

  1. One Model 151 Theremin
  2. Two plastic envelopes with one plate antenna in each (interchangeable)
  3. One plastic bag containing four hexagonal nuts for antenna attachment
  4. One Duracell 9V alkaline battery
  5. One Warranty Registration Card
  6. One Model 151 Theremin User Manual

Please retain the carton and all packing materials in the event the instrument has to be returned to Harrison Instruments for service.

Carefully remove the plastic wrapping from all items and inspect them for damage.

If damage is apparent:

RMA _____
PO BOX 9012

3. Additional Materials Required <back to contents>

The following items not supplied with the theremin are recommended for basic use:

4. Introduction to the Theremin <back to contents>

The theremin is named for its Russian inventor, Lev Sergeivitch Termen who developed the instrument in the early 1920s. It is one of the first electronic musical instruments, and has the distinction of being played by moving the hands within its proximity, without contact.

Theremins have two physical extensions called antennas. One of the antennas is used to control the pitch of the instrument's sound, and is referred to as the pitch antenna. The other is used to control the volume of the sound, and is referred to as the volume antenna. The pitch and volume produced by the theremin vary according to the capacitance between the hands and their respective antennas. The value of capacitance, in turn, is affected by the distance between each hand and its antenna.

The pitch-generating section of many theremins, including the Harrison Instruments Model 151, utilizes a principle called heterodyning, in which the signal from two inaudible, high-frequency oscillators are subtracted electronically to produce an audible difference frequency. One of the two high frequency oscillators provides a steady frequency, while the other oscillator's frequency is varied according to the change in capacitance between the hand and the pitch antenna. The volume-control section also uses changes in hand capacitance to alter the energy in a resonant circuit that, in turn, controls the loudness of the tone.

Many early designs of the theremin featured a vertical rod for the pitch antenna and a horizontal loop for the volume antenna. The 151 features two identical horizontal plates, one each for pitch and volume. The 151 also differs from traditional theremin designs in that the loudness of the tone increases as the hand is brought closer to the volume antenna, instead of becoming softer.

5. Model 151 Controls and Output Jack <back to contents>

The figure below identifies the front-panel features of the Model 151 Theremin. To provide visibility, the labels for the controls are located on the top of the instrument. The OUTPUT JACK is located on the rear panel.

Front Panel Features of the Model 151 Theremin

The following table describes the function of each feature.




Adjusts the response of the theremin's volume so that the tone is softest with the hand furthest away from
the volume antenna and loudest when the hand is just above the volume antenna.


Adjusts the theremin's maximum output volume.


Indicates when the instrument is on, and flashes rapidly when the battery is weak.


Turns the theremin on or off.


Adjusts the output tone characteristic from a low-harmonic, sine-like wave (fully counterclockwise position)
to a harmonically-rich wave (fully clockwise position).


Adjusts the response of the theremin's pitch so that the tone frequency is lowest with the hand furthest away
from the pitch antenna, and highest when the hand is just above the pitch antenna.

6. Battery Installation <back to contents>

The figure below is a top view of the Model 151 Theremin. The 9V battery, such as Duracell® type MN1604, is shown in the battery compartment with the cover removed. Note that the battery is installed with its terminals to the right and with its NEGATIVE terminal on top. The battery connector is snapped onto the battery with its wires also toward the top cover. The battery compartment cover is secured with two small slotted screws that may be removed with a standard, small-blade pocket screwdriver. To prevent damage to the instrument from possible leakage or corrosion, do not leave the battery in the theremin for extended periods of non-use. To prevent accidental battery consumption during shipment, the 151 Theremin is shipped with the battery uninstalled.

151 Theremin Battery Compartment

7. Setting Up the Model 151 Theremin <back to contents>

  1. Loosen the BASE LOCKING KNOB on the microphone stand and slide the legs to the bottom of the OUTER TUBE. Tighten the
  2. Fully extend the microphone stand LEGS and place the stand on a stable, level surface. Attaching the 151 Theremin to a Microphone Stand
  3. If the stand has a LOCKING NUT, turn it completely clockwise so that the COUPLING THREADS are exposed above it.
  4. While grasping the INNER TUBE to preventing it from falling into the OUTER TUBE, loosen the stand's height
    ADJUSTMENT COLLAR by turning it counterclockwise. The stand's INNER TUBE is now free to slide up and down.
  5. Continue to grasp the INNER TUBE with one hand while lowering the THEREMIN onto the top of the stand with your free hand.
  6. Engage the theremin's threaded ADAPTER with the stand's COUPLING THREADS.
  7. With the theremin perpendicular (90°) to the stand, slowly rotate the stand's INNER TUBE counterclockwise until it mates with the theremin's ADAPTER. Rotate the stand's INNER TUBE, and not the theremin, until it is tightly engaged with the ADAPTER.
  8. If the stand has a LOCKING NUT, tighten it by turning it clockwise against the ADAPTER.
  9. Adjust the stand's height so that the top of the theremin is at waist level. Firmly tighten the stand's height ADJUSTMENT COLLAR.
    NOTE: To prevent damaging the threads on either the microphone stand or the theremin, always engage the theremin to the stand at a perpendicular (90°) angle and support the theremin so that the angle is maintained as the microphone stand's INNER TUBE is rotated into the theremin ADAPTER. Never force the threads and never freely spin the theremin on the coupling threads, as doing so will ruin the adapter. To prevent excessive wear, occasionally place a small amount of light machine oil on the stand's COUPLING THREADS.
  10. The antennas supplied are identical and interchangeable and may be attached with either side up.
    Attach the VOLUME ANTENNA to the left side of the THEREMIN using two of the the four HEXAGONAL NUTS supplied. Hand-tighten the nuts securely. Do not use pliers. Repeat for the PITCH ANTENNA on the right side.
  11. Set the THEREMIN's POWER ON-OFF SWITCH to the "OFF" position (down).
  12. Insert one end of the (user-supplied) audio instrument cable into the theremin OUTPUT JACK and the other end into the (user-supplied) amplifier/speaker system.
  13. Set the theremin's front panel controls as follows:
    VOLUME ZERO:  Fully counterclockwise (Note: this control has ten turns)
    OUTPUT LEVEL:  9 o'clock position
    TONE:  Middle (12 o'clock) position
    PITCH  ZERO: Fully clockwise (Note: this control has ten turns)
    Perform the following steps with your hands or other objects away from the antennas:
  14. Set the amplifier volume control to its minimum level.
  15. Set the theremin's POWER SWITCH to the "on" (up) position. Note that the theremin's LED is illuminated.
  16. Slowly increase the amplifier's volume control to approximately one-tenth of its maximum range.
  17. Slowly turn the VOLUME ZERO clockwise until a tone just becomes apparent in the speaker.
  18. Turn the PITCH ZERO counterclockwise until the pitch of the tone begins to decrease. Continue turning the control just until tone becomes inaudibly low in pitch.

8. Playing the Model 151 Theremin <back to contents>

In the above procedure, the theremin was prepared for operation. However, a few more steps must first be performed before it is completely ready to play. First, it is important that the user is familiar with the following concept:

The output from the theremin is affected by the presence of any object, including any part of your body, within about four feet of either of its antennas. This means that your body position and body movement, and not just your hand positions, will affect the output pitch and volume. The player will not have exactly the same stance in front of the instrument each time, and the theremin's proximity to large objects such as furniture or walls will vary from one setup to another. Because of these factors, the theremin must be adjusted to compensate for these variations before it is played, as described in the following procedure.

In steps 1 through 3, the volume response will be adjusted:

  1. Stand directly centered in the front of the theremin, with your waist about six inches away. If you are using headphones, allow the cord to droop neatly downward from behind you, away from either antenna. It is important to remain still as you play because the proximity of your torso to the theremin will affect its behavior.
  2. Lift your left hand so that it is about one foot above the volume antenna. Note the volume level as your hand is lowered toward the antenna; the volume becomes louder as the distance between your hand and the antenna decrease. Touch the volume antenna with your hand and observe the volume. This is the loudest volume, and it may be adjusted with the OUTPUT LEVEL control. While still touching the volume antenna with your left hand, adjust the OUTPUT LEVEL control for a comfortable volume.
  3. Adjust the VOLUME ZERO control to obtain the following response:
    a) The output tone is not present with your left hand away from the antenna (your left arm at your side).
    b) The output tone just becomes apparent with your left hand about one foot above the volume antenna. Note that the volume control distance will become smaller as the VOLUME ZERO control is turned counterclockwise, and larger as it is turned clockwise.
    NOTE: A smaller volume control distance is suited to rapid staccato passages. Smoothly flowing, legato passages may be obtained with larger control distances.
    In steps 4 through 7, the pitch response will be adjusted:
  4. Purposely offset the VOLUME ZERO control by turning it clockwise so that a tone will be present, even without the left hand near the volume antenna.
  5. Lift your right hand so that it is about one foot above the right antenna (pitch antenna). Note that the pitch increases as the distance between your hand and the antenna decreases.
  6. Adjust the PITCH ZERO control to obtain the following response:
    a) The pitch is lowest with with your right hand about two feet above the antenna.
    b) The pitch is highest with your right hand about one inch above the antenna.
    Note that the pitch control distance will become smaller as the PITCH ZERO CONTROL is turned counterclockwise, and larger as it is turned clockwise.
  7. Readjust the VOLUME ZERO control to remove the offset that was applied in step 4.
    NOTE: To obtain more spacing between notes in the alto or soprano range, you may offset the PITCH ZERO control so that a middle pitch is obtained with your right hand away from the antenna. This will result in a smaller total pitch range, but will also provide more space between notes. Alternatively, shifting your stance so that you are slightly closer to the pitch antenna will also cause this offset to occur.

As with any musical instrument, individuals will develop their own particular style for playing theremin. As a general guide, it is suggested that the hands are positioned above the antennas with vertical movement used as the primary means of changing pitch and volume. Some lateral movement of the hands is natural and can be useful in avoiding the monotony of purely vertical motion. However, the player should watch their hands to prevent them from drifting too far from the optimal sensing area. Movements of the individual fingers of the pitch hand, a technique often used by thereminists playing "pole" type instruments, may also be employed when playing the 151 Theremin, although the intervals obtained for the same movements will differ for the two types of instruments.

It is not uncommon for beginning thereminists to become tired from holding their hands in position for extended periods, although they usually become accustomed after several sessions. Repeated, abrupt, jerking motions should be avoided because such motions may cause stress and injury to the joints. Since some repositioning of the body while playing is inevitable, it is recommended that the thereminist periodically check the response of the pitch, making sure that the lowest pitch is attained for a hand distance of about two feet. The high resolution and smooth operating character of the 151's PITCH ZERO control allows quick corrections to be made during a performance. While standing is traditional, the theremin may also be played comfortably while seated. In this case, a short microphone stand should be used with the 151 Theremin.

There are many practice methods available for the thereminist. The ability to recognize the actual pitch of a note (e.g. "A" or "A#") is not required, but the ability to maintain and repeat the interval relationships between notes is important. It is recommended that the beginner start by playing along to a recorded melody while concentrating on obtaining the corresponding hand positions. In initial exercises, it is desirable to concentrate just on the pitch hand, while simply maintaining a fixed distance with the volume hand. The ability to use the volume hand to emphasise individual notes and provide the all-important dynamics of loudness will be attained intuitively once the student is comfortable with pitch control.

The rapid, cyclic motion of the pitch hand to create vibrato is a common technique. In this manner, the optimal desired pitch may be included within the extents of the vibrato range, therefore attaining the "perfect" pitch, at least momentarily. Vibrato typically spans the range of a quarter-tone to a full-tone interval and is an effective way to enhance technique. However, the ability to attain correct pitch with practically no vibrato is also a desirable skill. The same cyclic motions applied to the volume hand can also be used effectively for tremolo.

Recording your theremin sessions is an invaluable tool for improvement. After several practice sessions, it is suggested that the student play back a solo of moderate length and observe the accuracy of the pitch intervals and ability to maintain the desired key. Improvement may also be attained by accompanying other instrumentalists. It is suggested that beginners find group opportunities without a vocalist, since the theremin may likely be used to play melody and possibly "compete" for the vocal range. One of the advantageous features of the 151 Theremin is its capability to produce bass tones, which may add a valuable element to the overall mix. While the theremin is often used for lead lines, it can also be used effectively in harmony or as backup.

The prospect for adding special effects to the theremin is limitless, but it is recommended that beginners first concentrate on playing "dry," perhaps with a small amount of reverberation added to provide presence. Reverberation also provides a small amount of persistence that some players find useful for attaining accurate intervals. While, historically, the theremin has been used to provide non-melodic sound, as in the stereotyped use for "special effects" in film, it is also capable of providing the means for articulate, accurate melodic work, given proper attention and adequate skill.

9. Grounding and Portable Operation <back to contents>

A proper earth ground is essential for the 151 Theremin to operate predictably and provide the benefits of its full pitch and volume sensing distances. In mains-powered installations, the theremin receives its ground through the audio instrument cable that connects the theremin to the amplifier/speaker or mixing console.

Portable operation does not provide the convenience of such a direct ground connection. However, the proper configuration of the audio instrument cable that connects the theremin to the amplifier/speaker can readily provide an adequate substitute. To achieve this, it is recommended that the cable, such as the recommended 15-foot Whirlwind® model number SN15, be laid in an approximate circular pattern immediately around the feet of the theremin stand and the player. Spread the cable out in a small area immediately in the vicinity of the stand to ensure that there is adequate capacitive coupling, and therefore grounding of the theremin, to the surface shared by the player and the instrument. The exact lay of the cable is not critical, but it is important not to "bundle up" the excess cable in one spot.

Note that specific adjustment to the VOLUME ZERO and PITCH ZERO controls must be made each time the theremin is relocated. Part of these adjustments address differences in the effectiveness of the grounding among different locations. For example, the optimal settings of the ZERO controls will change by several full rotations for a 151 played in a recording studio in a steel-frame and concrete building, compared to one played through a battery-powered portable amplifier/speaker on a wood stage situated on a dry, sandy terrain.

Although many portable amplifiers provide multiple instrument and mic inputs, it is important that your portable unit be specifically dedicated to the theremin alone. This is because the variations in ground coupling from other inputs, for example, a guitar that is being moved while played, will affect the pitch and volume of the theremin.

Do not place cables connected to this product in areas where they can cause a trip hazard.

10. Tone Control <back to contents>

The TONE control on the 151 Theremin provides a wide variety of sound qualities. When fully counterclockwise, the theremin's tone will be sinewave-like, mostly devoid of harmonics. The fully clockwise setting of the TONE control will produce a wave similar in qualities to a full-wave rectified sinewave, which is harmonically rich. Between these two extremes, a variety of tone qualities are available, including some that are similar to many other types of theremins.

CAUTION: Low-pitched tones, especially sinewaves, do not seem loud, but they may produce sufficient power to cause damage to amplifiers and loudspeakers. When setting up the theremin, always start with your amplifier/speaker system volume control settings at low levels to prevent damage. It may be desirable to use an equalizer and/or limiter at the theremin's output to match the performance of your audio system.

NOTE: The degree of pitch accuracy attained by any particular thereminist, actual or perceived, may vary depending on the tone of the theremin. In some instances where a high-level accompaniment or high ambient noise is present, the thereminist may elect to adjust the tone for a more sine-like quality so that most of the sound energy is in the fundamental region, therefore making it easier to attain the correct pitch. Many other factors also contribute to what tone may be most appropriate; for example, a sine-like tone, dissimilar to the sounds produced by most conventional instruments, may "stand out" too much in a mix, creating a sense of incompatibility with other instruments.

11. Model 151 Theremin Specifications <back to contents>

Useful pitch range Five octaves (55 Hertz to 1760 Hertz)
Available pitch range Seven octaves (27 Hertz to 3520 Hertz)
Nominal pitch sensing distance 18 inches
Pitch response Frequency increases as hand distance decreases
(View Graph)
Tone waveform characteristic range: Sine-like wave to fully-rectified sine-like wave
Volume dynamic range 62dB minimum
Nominal volume sensing distance 14 inches
Volume response Volume increases as hand distance decreases
(View Graph)
Control compliment Volume Zero (10-turn potentiometer)
Output Level (1-turn potentiometer)
Power Switch
LED Power and Low Battery Indicator
Tone (1-turn potentiometer)
Pitch Zero (10-turn potentiometer)
Output connector 1/4" Mono Phone Jack for standard audio instrument cable
Output impedance Approximately 900 Ohms
Maximum output level 3 Volts Peak-to-Peak
Power source One IEC 6LR61 9V Alkaline Battery,
Duracell® MN1604 or equal
Battery life (active or idle) 24 hours, minimum
Operating temperature range 30°F to 100°F
Storage temperature range -10°F to 120°F
Overall dimensions (without antennas): 17"L x 8"W x 3"H
Overall dimensions (with antennas): 26"L x 8"W x 3"H
Antenna dimensions 5.5" x 8" Rectangular Plates
Weight Approximately 3.5 Pounds
Shipping weight Approximately 4.3 Pounds

12. Troubleshooting Guide <back to contents>


Possible Cause

Recommended Action

The LED does not illuminate when the POWER SWITCH is in the "UP" (on) position. The battery is dead or weak. Replace the battery.

(Refer to Section 6, "Battery Installation.")

The battery connector is not making proper contact. Examine the terminals on both the battery and the battery connector and gently reshape both female terminals by slightly squeezing their edges together.
The LED flashes rapidly. The battery is weak. Replace the battery within an hour of further use.

(Refer to Section 6, "Battery Installation.")

There is no sound from the speaker. The LEVEL control on the theremin is set too low. Turn the theremin LEVEL control clockwise.
The volume control on the external amplifier or external sound system is set too low and/or an input selector switch is set incorrectly. Increase the volume and/or gain of the external amplifier or sound system;
check relevant selector switch positions.
The audio instrument cable connecting the theremin to the external equipment is defective. Replace the cable with a known-good one.
The sound is distorted. The LEVEL control on the theremin is set too high for the external amplifier or sound system. Reduce the theremin output by turning the LEVEL control counterclockwise until the sound is undistorted.
The gain and/or volume control on the external amplifier or external sound system is set too high. Reduce the gain and/or volume of the external sound system.
A decrease, instead of increase of pitch occurs as the hand is brought closer to the pitch antenna. The PITCH ZERO control is not adjusted properly. Turn the theremin ZERO controls clockwise until the desired response is obtained.

(Refer to Section 7, "Setting Up the Model 151 Theremin,"and Section 8, "Playing the Model 151 Theremin.")

The pitch scale is constrained within too short a range of hand positions. For example, the lowest pitch occurs when the hand is 5 inches away from the antenna.
The volume range is constrained within too short a range of hand positions. For example, the volume range begins when the hand is 5 inches away from the antenna. The VOLUME ZERO control is not adjusted properly.
No tone results even when both hands are brought very close to the antennas. The PITCH and/or VOLUME ANTENNA nuts are loose Hand-tighten all four nuts securely. (Do not use pliers.)
The tone and/or volume abruptly shifts dramatically.
The note positions change while the theremin is played. There are variations in your body position. Hold your body at a consistent distance from the theremin, and only move your hands up and down above the antennas.
Objects are being moved in the proximity of the theremin. Eliminate moving personnel and objects within a four-foot proximity of the theremin, or move the theremin to a less-trafficked area.
Sporadic pitch shits are evident in the pitch of the tone, even when the hands are held steady. There is interference from a nearby electronic device and/or another theremin. Move the theremin to a different area.
There is a persistent "fluttering" of the pitch of the tone and/or the volume level.
When used with a battery-powered amplifier/speaker, the PITCH ZERO control can not be adjusted adequately to obtain a useful scale; the scale is constrained within too short a range of hand positions even when the PITCH ZERO control is fully clockwise. There is an inadequate ground connection. Refer to Section 9, "Grounding and Portable Operation."
When used with a battery-powered amplifier/speaker, the VOLUME ZERO control can not be adjusted adequately to obtain a range; the volume range is constrained within too short a range of hand positions even when the VOLUME ZERO control is fully clockwise.
A pitch change occurs when the volume hand is moved, even when the pitch hand is held steady.
People have an annoyed expression when they hear you play. Your pitch is too inaccurate. Practice attaining adequate pitch recognition and control.

Do not despair, because the times when you feel you are making the least progress are probably when you are actually learning and improving the most.

You are playing too loud for them. Reduce the theremin output by turning the LEVEL control counterclockwise.
They dislike the tone quality. Change the tone quality with the TONE control. Setting the control control in a range between 9 o'clock an 3 o'clock will produce less obtrusive tones. In general, the extreme counterclockwise position will produce a tone that is most subject to criticism.
Those people have no general appreciation for music. Find more appreciative people.

13. Model 151 Theremin Warranty and Repair Service <back to contents>

Harrison Instruments Two-Year Limited Warranty

Harrison Instruments Corporation ("Harrison Instruments") warrants this product to be free from defects in materials and workmanship for a period of two (2) years from date of purchase, PROVIDED, however, that this limited warranty is extended only to the original purchaser and is subject to the following conditions, exclusions and limitations hereinafter set forth:

This limited warranty shall be void and of no effect, if:

  1. The first purchase of the product is for the purpose of resale; or
  2. The original purchase of the product is not made from Harrison Instruments; or
  3. The product has been damaged by accident or unreasonable use, neglect, improper maintenance, or other causes; or
  4. The serial number affixed to the product is altered, defaced, or removed; or
  5. The product's enclosure is opened by any party not authorized by Harrison Instruments.

In the event of a defect in materials or workmanship covered by this limited warranty, Harrison Instruments will repair the defect in materials or workmanship without charge or replace the product, at Harrison Instruments' option, provided however, that in any case, all costs of shipping for the purpose of shipping the product to Harrison Instruments for repair are paid by you, the purchaser.


In order to obtain service under this warranty, you must:

  1. Contact Harrison Instruments and obtain a Return Materials Authorization (RMA) number.
  2. Ship the defective product, FREIGHT PREPAID and INSURED for its purchase value, to:

    PO BOX 9012

  3. Include a complete, detailed description of the problem.
  4. Include a complete return address.

If the defect can be remedied under this limited warranty and other terms and conditions expressed herein have been complied with, Harrison Instruments will provide the necessary warranty service to repair or replace the product and will return it to you, the purchaser.

Limitation of Liability

Harrison Instruments' liability to the purchaser from any cause whatsoever and regardless of the form of action, including negligence, is limited to the the amount of the original purchase price of the product that caused the damage or that is the subject of, or directly related to, the cause of action.

Harrison Instruments does not assume liability for personal injury or property damage arising out of, or caused by, any or all alterations or attachments to its products, nor does Harrison Instruments assume any responsibility for damage to interconnected non-Harrison Instruments products that may result from the normal functioning and maintenance of Harrison Instruments products.

14. Contacting Harrison Instruments
<back to contents>

Contact Harrison Instruments by e-mail at

or in writing at:

PO BOX 9012

(Back to 151 Theremin product description page)

Copyright Notice: This manual, either in electronic or printed form, ©2008 by Harrison Instruments, Incorporated.
Harrison Instruments, Incorporated reserves the right to make changes to this manual without prior notice.

Publication Number 151UM-1
Rev. 3  08-01-2014