Hi,

I'm controlling the pitch of an MS-20 synthesiser with a control voltage varying from 1 to 2 volts using a potential divider with resistors in series corresponding to notes in a musical scale. I touch the switch to a corresponding resistor value close the circuit and it plays a note. My problem is that when I open the circuit again my voltage out drops to 0V.

Is there a way to design a circuit that would hold a steady voltage when I disconnect the switch until a new voltage above 0 is presented?

 

For how long must it hold the voltage?

 

For how long must it hold the voltage?

forever would be ideal but 10 seconds would work and it must change to a new value if a new voltage between 1 and 2 is given.

 

You need a sample and hold circuit with a time constant of 20-50 seconds.
Hence an opamp buffer feeding an RC integrator where R = 1MΩ, C = 47μF followed by a high input impedance FET opamp.

 

forever would be ideal but 10 seconds would work and it must change to a new value if a new voltage between 1 and 2 is given.

Oh, I did not see the "forever" requirement.
In that case, omit the discharge resistor R and reduce C to the minimum to get the desired hold time.