Synthesiser keyboard - cant work out how to hold notes after trigger

[george2525]

Ok so ive been making a synthesiser keyboard. Ive got it working, the notes are more or less in tune and it sounds nice.

My problem is that it plays a note when no key is being pressed. This is the default oscillator frequency that is present when no control voltage is applied.

I need it to hold whatever note was last pressed so that when all keys are released it doesn't revert back to the default tone.

I have been looking at sample and hold. RS flip flops, latches and that type of thing but im lost as to which method to research. I have not managed to find any examples that reference this problem which is making it extra difficult.

If I use some kind of sample and hold, it needs to be very accurate because the control voltages are very precise and so if i use op amps etc they need to buffer the control voltage precisely.

obviously when the keys are released I dont want the default tone to be held!

so I think I need something that holds the last note whenever the control voltage is approximately 0V , say less than 0.05V or so. IE whenever there is no control voltage, the last voltage is held.

I hope this makes sense.

Im not asking for full schematics or anything, just to be pointed in the right direction.

Thanks

 

[tedstruk]

you have to make the entire board into a trigger system. after all its called a KEYBOARD.
now don't take me as a tech.... I'm a really bad hack@electronicspoint
so I would build a simulator keep the notes on, then I would attach a second circuit that fires a switch that acts like a note signal, but with a do nothing app like turns on an LED that says "no note to play" under it