Tempo enhancement device
United States Patent 3865001

An electromechanical apparatus accompanies rhythmic human movement with music of appropriate tempo. This is accomplished by monitoring the activity with a transducer attached to a supporting structure, which will move in response to shifts in human weight. These peaks are counted and the measured count is used to control the relative volumes of a multiplicity of differently paced musical tracks.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
84/602, 84/741, 84/DIG.1, 84/DIG.27, 984/344, 984/347
International Classes:
G10H1/32; G10H1/40; (IPC1-7): G10H3/00
Field of Search:
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Primary Examiner:
Wilkinson, Richard B.
Assistant Examiner:
Witkowski, Stanley J.
Parent Case Data:

This application is a continuation-in-part of application Ser. No. 174,464, filed Aug. 24, 1971, and now abaondoned.
What is claimed is

1. In a device for changing the relative volumes of at least two sources of differently paced musical selections in response to the tempo of movement of a supporting structure caused by shifts of human body weight;


This invention relates to an apparatus for automatically sensing the tempo of some form of human activity and enchancing its rhythm by actuating appropriately paced musical accompaniment.

In various situations it often is desirable to enhance the tempo of some rhythmic activity such as dancing, gymnastics, trampoline acrobatics, or exercising. Accompanying sound adds another dimension to the activity, increasing the awareness of its rhythm for the participants and spectators. Such accompaniment could previously be obtained only through manual control of the music. With this invention the control is automatic. By eliminating the manual operator labor costs are saved, privacy is increased, and the activity is more directly linked to its accompaniment.


Each type of rhythmic human activity generates some movement of the supporting structure which can be instrumented by an appropriate form of transducer, producing a time-varying voltage. The type of activity dictates the most efficient transducer for monitoring. Typical transducers that may be used in various embodiments of this invention include accelerometers, spring-loaded contacts, strain gauges, and conducting rubber rheostats. For instance in monitoring dancing or gymnastics a vibrational transducer in contact with the floor or mat such as an accelerometer could be used.

This invention comprises a unique electro-mechanical network which responds to the repetition rate of the motion. This is transformed into the repetition rate of a voltage through the use of a transducer. The repetition rate of the motion is counted, and this count is used to select the relative volume for each of a multiplicity of differently paced music tracks.

An embodiment of the invention will now be described with reference to the appended drawings.


FIG. 1 is an external view of the apparatus, showing how it may be used in conjunction with a home stereo tape recorder system.

FIG. 2 is a schematic diagram showing the electromechanical network utilized in the embodiment.

FIG. 3 is a schematic diagram of the detail of the digital-to-analog network.

FIG. 4 is a circuit diagram showing the detail of the differential amplifier circuit.


In FIG. 1 the transducer 1, in this case an accelerometer is shown monitoring an activity. The electrical signal from the transducer is processed by the circuitry to be described, which is a modification of a home stereo amplifier unit 2. The input to the stereo amplifier consists of a home stereo tape recorder 3 playing a special stereo tape 4, whose first channel consists of slow music and whose second channel consists of appropriately syncopated fast music. The stereo amplifier unit 2 sets the relative volume of the music from the two tape tracks. A slow tempo in the monitored activity causes the amplifier 2 to make the slow track louder compared to the fast track. Similarly for a fast tempo activity the sound of the faster musical background predominates. The music from the two tracks, with their relative volumes thus regulated, issues forth from the two speakers 5 and 6, respectively.

Referring to FIG. 2, the schematic of the electromechanical network is shown. The signal produced by the transducer 1 is a time-varying voltage with its peaks corresponding to the peaks of the movement being monitored. These peaks occur when the shifting body weight causes the supporting structure to make excursions above and below its equilibrium position. The signal from the transducer is amplified by a standard electronic amplifier circuit 8. This amplified signal is input to the pulse shaper circuit 9, which forms a pulse from each peak of the signal. These pulses control a digital-to-analog network circuit 10 which generates an analog voltage proportional to the time between pulses. The output of the digital-to-analog network 10 forms the input to the differential amplifier circuit 11. The left and right channels of a home stereo amplifier constitute the slow and fast channels 12 and 13, respectively. The differential amplifier circuit 11 uses this voltage from the digital-to-analog network, proportional to the period of pulse repetition to control the slow (left) channel amplifier 12 and the fast (right) channel amplifier 13 of the home stereo amplifier. This is done by biasing a stage of amplification of each channel with voltage from differential amplifier, adjusting the balance of volume between these two channels. If the voltage from the digital-to-analog network 10 is equal to a preset level corresponding to an intermediate speed pulse rate reference, the sounds will be balanced in both channels. If the pulse rate is higher than the preset level, the volume will be concentrated in the fast channel; if less, it will be concentrated in the slow channel. The right and left channels of the tape recorder output 14 and 15, which were derived from the special stereo tape 4, are then amplified by the right and left channel amplifiers 12 and 13 of the home stereo amplifier. Since the balance of the volume between these amplifiers 12 and 13 has been adjusted on the basis of the period of pulse repetition, the amplification of the fast track channel will be greater if the pulse repetition rate is faster than the reference rate and the amplification of the slow track channel will be greater if the pulse repetition rate is slower than the reference rate. The audio signals from the amplified musical tracks then go the speakers 5 and 6. If the sensed motion is slow in tempo then the sound from the slow channel speaker 5 will be louder and predominate, and if the sensed motion is fast in tempo then the sound from the fast channel speaker 6 will be louder and predominate.

The detail of the digital-to-analog network is shown in FIG. 3. The purpose of this network is to determine the time period between successive pulses and put out an analog voltage proportional to this period, and thus inversely proportional to the pulse repetition rate. Incident pulses from the pulse shaper reset all the elements of the digital-to-analog network and direct the set of logic 19 to permit a train of pulses from the clock 18 to be counted in the binary counter 20. When the next incident pulse occurs, the contents of the binary counter are transferred to a storage register where they are converted to analog form by the digital-to-analog converter. Since the rate of the clock is known, the time period between successive pulses can be determined by the count accumulated by the counter during the period. The process of counting can, therefore, continue for the next time interval, the value of the count for the previous interval being stored in the register. When the pulse occurs, the second counter number will be read into the register 21, erasing the existing contents and converting it to analog via the digital-to-analog converter 22. The output of the digital-to-analog converter 22 is a voltage proportional to the period. This voltage is then put through the low pass filter 23 before being fed to the differential amplifier circuit.

FIG. 4 shows the differential amplifier circuit consisting of a subtractor amplifier and an inverter. The subtractor amplifier portion consists of operational amplifier 24, associated resistors 25 and 26, dc bias voltage source 27, and potentiometer 28. The inverter portion consists of operational amplifier 29 and associated resistors 30 and 31. The filtered analog signal from the digital-to-analog network is compared to the preset reference voltage level of the potentiometer 28, which establishes the balance position for the period of repetition. This reference voltage corresponds to the voltage that would come from the analog-to-digital network for an intermediate speed pulse repetition rate. The subtractor amplifier produces a voltage proportional to the difference between the reference voltage and the analog input. This voltage determines the magnitude of voltage biasing a stage of amplification of the fast channel of the stereo amplifier and thus controls its gain. To obtain the algebraic negative of the output voltage from the subtractor amplifier it is fed to an inverter, consisting of operational amplifier 29 and resistors 30 and 31. This results in a voltage equal to the difference between the analog input and the reference voltage which goes to the slow channel of the stereo amplifier. If the analog input is larger in absolute value than the reference voltage, the voltage to the fast channel amplifier will be negative and the voltage to the slow channel amplifier will be positive. Both voltages will be proportional to the difference between the analog input and the reference. Conversely if the analog input is less than the reference voltage the voltage to the fast channel amplifier will be positive and the voltage to the slow channel amplifier will be negative.

To obtain more than two speeds of background music additional channels may be used with a device for selecting among the channels. If enough additional channels are used an almost continuous range of background music speeds can be obtained.

All that has been said with reference to a tape music reporduction system could also be accomplished with a disc or some other form of music reproduction system.

It is also possible to augment the sound with a light display of various colors corresponding to various pulse repetition rates. This can be accomplished by having bulbs of various colors light in response to various levels of voltage measured at the output of the low pass filter 23. One means of switching the bulbs is with a control circuit such as described in U.S. Pat. No. 3,480,912 to S. D. Speeth and P. C. Norem. Further rhythm accompaniment can be obtained by triggering a rhythm instrument with the peak values of the electrical signal from the transducer. Other modifications will be obvious to those skilled in art.

The invention is not limited to the exemplary construction shown above, but may be made in various ways within the scope of the following claims.