<html><body style="font-family: Helvetica,Arial,sans-serif; font-size: 12px;">I think they are essentially the same as old organs - the basic approach is to generate a square wave for each note, then optionally use a fixed filter (often just a resistor and a capacitor/inductor) to produce various different tones, then optionally combine those tones for each key to produce different timbres. The details of how this is done (which is what you're actually asking about) varies from machine to machine - older designs used multiple poles on the key switches to allow the tones to be combined; newer designs used note keying chips which did the combining internally. There are almost certainly other techniques I don't know about.<br><br>Many stringers also had effects such as phaser circuits, BBD-based chorus, and vibrato (achieved by varying the clock on the top octave generators) to produce the classic "string machine" sound.<br><br>Fun fact: some organs produced white noise for their drum machines by combining many unrelated (dissonant) tones (somewhat like the TR606/DR-110 cymbal sound that was generated by combining 6 square wave oscillators).<br><br>The one thing I haven't been able to fully understand is how they did fully polyphonic A/R envelopes. I've been meaning to have a look at some schematics at some stage but haven't gotten around to it yet.<br><br>Cheers,<br>A.<br><blockquote><br>----- Original Message -----<br><div id="origionalMessageFromField" style="width:100%;background:rgb(228,228,228);"><div style="font-weight:bold;">From:</div> "Elain Klopke" <functionofform@gmail.com></div><br><div id="origionalMessageToField" style="font-weight:bold;">To:</div><synth-diy@synth-diy.org><br><div id="origionalMessageSentField" style="font-weight:bold;">Cc:</div><br><div style="font-weight:bold;">Sent:</div>Sun, 19 Feb 2017 15:31:17 -0600<br><div id="origionalMessageSubjectField" style="font-weight:bold;">Subject:</div>[sdiy] questions on string synthesizers<br><br><br><div dir="ltr">How do the selectors for the various sounds work? Like with the violin and cello, trumpet and tuba tabs or stops, you press the button and you hear an aproximation of a violin sound, and you can add in the rest of the sounds to get something orchestral. How is the string synth taking the raw output from the top octive chip and subsequent dividers and transforming it into the various instrument sounds? I assume there's some sort of filtering going on, but I can't quite wrap my head around it.<div><br></div><div>thanks,</div><div><br></div><div>-Ian</div></div>
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