Brooke Clarke 2003 - 2016

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    DIY Synthesizer

Yamaha DX7 II Analog Music Synthesizer

The DX7 (Wiki) uses a very sophisticated analog mixing scheme to make very complex and pleasant to humans sounds.  It's probably the last of the analog electronic music instruments.

In addition to equal temperament tuning there were other tunings built in:
Vallotti & Young                 
1/4 Shifted equal  
1/4 Tone              
1/8 Tone


3577084 (Google)Computer Sound Generator May 4 1971 Singer-General Precision 327/107; 84/659; 327/134; 341/147; 377/51; 377/112; 984/389; 984/DIG1
3696201 (Google) Digital Organ System 84/648; 84/659; 84/660; 984/382; 984/DIG1 (Wurlitzer) -
4018121 (Google) Method of synthesizing a musical sound Filed: May 2, 1975, Pub: April 19, 1977 John M. Chowning 84/696; 84/101; 84/659; 984/309; 984/324; 984/389; 984/DIG1 - Basis of the Yamaha DX-7 Synthesizer.
Patents calling 4018121 -
4813326 Method and apparatus for synthesizing music tones with high harmonic content, Yamaha, Filed: Jul 16, 1984, Pub:  - Fig 22 block diagram of an operator
4922795 Tone signal forming device, Yamaha, Filed: Nov 17, 1987 -
5025702 Electronic musical instrument employing time-sharing frequency modulation and variable control of harmonics,Yamaha, Filed: Jul 3, 1975, Jun 25, 1991 - FM synth (filed a month after Chowning)
5191161 Electronic musical instrument including waveshape memory and modifiable address control, Yamaha, Filed: Jul 3, 1975, Pub: Mar 2, 1993 - variable color with same pitch from table entries.

DX-7 II + add on

I had one of these synthesizers.  After adding on a small PCB (Grey Matter E! ?) the capabilities were greatly increased and not only could it be controlled by my Radio Shack Color Computer it also could remember an arrangement.  I think it had a complex rendition of "The Entertainer" built-in.  If you know the maker and/or model number of this add on board let me know.
Wave of the Future - History of Chowning's development.

With the introduction of micro controllers and home computers the age of digital sampling (Wiki) allowed the production of sound that matched that of an actual instrument.  The samples could be played back at different speeds and modified using the same signal processing methods used for analog music synthesizers.  So analog synths fell out of favor and the digital synths took over.

But in the late 1990s an interest in analog synths came back.  Part of this is related to the availability of Eurorack (Wiki: Doepfer_A-100)modules, most of which are reasonably priced.  PAiA (home, Wiki) has been making low cost music synth modules since 1967 and still offers them.

Yamaha TX802

Is a keyless rack mount box version of the DX7.  Requires external MIDI controller.
YouTube: Yamaha TX802 Demo - Yamaha TX802 - A few performance patches -

Dave Benson's DX7 Page - many documents
Fig 1
Hold number pad 8 and 9 while turning on power.
Firmware V1.0 22-APR-87
Yamaha TX802
Fig 2 Op Sys chip in upper right
just below TX802, marked: XB223 [8]
New chip marked: TX802, XB224 OS V 1.5
Yamaha TX802
Fig 3 with Ver 1.5 op sys:
The top LCD row is all black dots.
Yamaha TX802

Theremin (Wiki) (my Geek Stuff page)

There is an interesting Video about Leon Theremin: Theremin: An Electronic Odyssey 1993 (IMDB, Netflix)
He's the father of electronic music.  That's to say he made the first electronic music instrument.  Moog (Wiki) designed a number of Theremins starting in high school.  The Beach Boys (Wiki) used a Tannerin (Wiki) (easier to use than the Theremin), for Good Vibrations. PAiA and Korg make Theremins.

TED Talks:  Pamelia Kurstin plays the theremin - her's is a left handed unit, i.e. she uses her left hand for pitch control.  She makes the point that when playing you must keep your body very still, even to the point of not breathing during a low note.

The problem is most people can not move their hand to a fixed position in 3D space and hold it there, so it's a difficult instrument to master.


This introduced me to expressive music controllers.  Each key is sensitive for pressure (Z axis), pitch bend (x axis) and a third parameter like filter setting (y axis) allowing for very nuanced performance.

There are a number of other expressive controllers such as:
The Eigenharp family of instruments from EigenLabs - patent 8934088 Sound-creation interface - uses a custom switch that has variable outputs for x, y and z based on modulating a light beam or using a breath controller


Korg MS-20 Mini Synthesizer

While looking for an analog music synthesizer that might be used with the Linnstrument came across the 1978 MS-20 (Wiki) and the modern MS-20 Mini version that includes MIDI (Wiki).
Note that the M-20 is a monophonic (one note at a time) synth and so is not suitable for use with the Linnstrument.

Korg SQ-1 Analog Sequencer

Pocket Operators by Teenage Engineering

Gecho Loopsynth

DIY Synthesizer


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Page created 22 June 2003.