The trigger circuit

OK, how will we trigger these waves ?
I tried several circuits and came up with a very compact solution.
A MOSFET transistor serves as trigger and envelope gate.
This handy MOSFET has 2 gates ; 1 gate will amplify the sawtooth and the other gate will be used to control the envelope of the sound.
A simple RC circuit controls the ATTACK and RELEASE time.
I will add the schematics later for a better understanding