the LM567 seems perfect for the job.
but if i got 10 tones from ten different keys, does it mean that i need 10 LM567 ?!?!
or is there a chip with multi tones and consequently multi outputs?
what about connecting a binary counter to a transistor which will play the role of the variable resistor; now the counter would be synchronised with the pic micro so as it scans through the desired range of frequencies
thanks for your help, but before this, i have another project to finish