I think I might try this... becasue I can

[MikeH]

I was disassembling a non-functioning keyboard today to see if there was anything of use in there, which there really wasn't, but it is full of all these nice momentary switches for the keys.  And then the offset of the keys between rows made me think of a keyboard- like, a piano keyboard.  Hmmm...  Could it be done?  I was thinking I could use a 555 timer as a tone generator for each note, and layout about an octave and a half (which would be about 18 555s, or 9 556s) and do a simple mixing at the output of all the notes.  It would obviously be not-all-too useful and sound like hell... but I would like to try it, just to see if I can.

[frequencycentral]

The classic way to do it would be to make 12 'top octave' tone generators and use 12 CD4013 to get the next two octaves down!

[MikeH]

You mean like an mxr blue box?

[frequencycentral]

Yup, like 12 blue boxes. Each 4013 can divide by 2 (-1 octave) and by 4 (-2 octave). Strictly square waves though. But you would have 36 note polyphony. A bit like the old EML Polybox.

[David]

The classic way to do it would be to make 12 'top octave' tone generators and use 12 CD4013 to get the next two octaves down!

Once upon a time, there was a chip that would generate all 12 tones for you.  That chip, if you can find it, is probably up past $50USD now.

[MikeH]

I don't know, that might be cheaper than a 555 and a trimpot for each note...

Make me think though; What would be the most economical way to do the tone generating?  Obviously I was thinking a 555 with a fixed resistor and a trimpot to dial in (aka "tune") each note.

[R.G.]

555s are not stable enough to use for musical note generation. They drift, as do all R-C oscillators. You need at least L-C frequency setting, and better yet crystal controlled.

The classic way to do it would be to make 12 'top octave' tone generators and use 12 CD4013 to get the next two octaves down!

Once upon a time, there was a chip that would generate all 12 tones for you.  That chip, if you can find it, is probably up past $50USD now.

Yep, the MK50240.

You can do most of that now with a $2.00 PIC driving a set of CD4024 dividers and a CD4046 PLL per note. That setup generates all the notes of the entire musical scale, 96 notes. You can use shorter dividers than the 4024 if you like and might cut down on the number of chips. Sounds complicated, but really it's just repetitive - same circuit every note, 12 times.

[sean k]

Why not go the 1volt per octave route of synths and have the resistor dividers between notes and just the one VCF with a tempco and some matched transistors. Theres lots of stuff out there to do that and it an inroad straight into the weird and wonderful world of analog synthesis.

[MikeH]

You can do most of that now with a $2.00 PIC

What's a PIC?

[zyxwyvu]

What's a PIC?

http://www.google.com/search?q=pic
http://en.wikipedia.org/wiki/PIC_microcontroller

[MikeH]

http://www.pic.com/