At the moment I have no sound recordings (only captured the pin levels in audio mode by logic analyzer) but did some video including sound that is still in the digicam. (I will put it on a file hoster when I get it downloaded on the laptop.)
The default synth (press 'musical note' and any key except 'F') should sound like a guitar (fast attack, then decaying within about 0.7s). Enter now 'F' '0' 'C' to disable the envelope, which turns it into a steady toot at 100% volume (stays on so long the note key is held). Pin 10 apparently charges the volume capacitor to 100% at begin of any note.
The total volume and decay level also strongly changes with battery voltage. With full batteries it can be unpleasantly loud, and sounds decay slower and some less low (i.e. louder ADSR "sustain" phase). The "attack" and "release" phase of ADSR are not adjustable. So this should be an analogue parameter (like a channel volume control).
The "race car" volume decays to zero when holding the button (car drives away). Also "helicopter" gets quieter and louder again in a loop when holding its button. Also the "bee" grows quieter and louder with button held.
