This sound effect circuit is from a Radio Electronics magazine from December 1969. The transistors support equivalents and the power is provided by a battery to reduce the possibility of noise.
We found this circuit in an American 1980s documentation. The operational ones used are not common...
This filter with the 741 op amp was found in the February 1995 Electronics Now magazine. The power...
With two cascading tunnel diodes, this circuit found in a 196 General Electric documentation...