This circuit was found in a 1991 PE Hobbyst Handbook. The components are still common and each note has an individual adjustment.
In fact, this circuit from the 60's applies to photographic printers of the time, timing the...
We found this circuit in the April 1993 Electronics Now magazine. Almost any general-purpose JFET...
In an English magazine from 1977 we found this interesting touch bongo circuit that can be mounted...