i started by build the square wave generator using a 555 timer, using a schematic online for a near 50% duty cycle, anf changes frequecy based on C and the r2, i got stuck here trying to do the math to see what resistace is needed for the frequencies im looking for (261.63 Hz, 293.66 Hz, 329.63 Hz, 349.23 Hz, 392.00 Hz, 440.00 Hz, 493.88 Hz)