Analog tuner idea

[Martin Czech]

Some custom modulars have a quartz frequency/time normal.
I remember an old "Funkschau" circuit which was a tuner for
acoustic instruments. They used a quartz osc, divider und then
freq multiplier with 4046 pll and 4051 four digit bcd divider
in the loop. Together with 4 digit bcd switches (the 0-9 style)
one could select key frequency. Divide by 2 gives octaves.
They also used 4046 with open loop to have a "too low" or 
"too high" display, which is usefull some times.
After tuning a while one ,tends to get tired, it would be difficult
to hear , if you are too low or not without display.
They claimed that this circuit would work even with piano/microphone.

If you use exor for beat freq exageration, this should be ok for acoustic
control at all frequencys (cheap ring mod or "multiplier").
I don't think that you need sine wave conversion in this case.
How many harmonics of a squ can you hear at high freq ?
I can't tell if its saq tri or sqa at say 13kHz already.

m.c.