based on that, would i be right in saying that the 20k variable resistor in the bottom right would control volume?
And if you were to add a button right after the variable resistor, would that work like hitting a key on a keyboard to initiate the sound (press and hold the button and the sound starts, release the button and it stops)
This circuit has a digital square-wave output with the volume fixed by the supply voltage. It could feed a volume control that feeds a linear power amplifier circuit.
The 20k pot adjusts the frequency of its internal oscillator. When it is close to the frequency of the variable oscillator then the sound frequency is very low or is turned off.