This organ, played by a probe was found in no old documentation, but it can be easily implemented these days. The integrated circuits are 555. The trimpot allows individual tuning of the keys.
This Rytron transmitter was published in a 1953 book. The circuit can be implemented with a BC558...
Foto-Darlington for applications such as light sensor. In normal applications only the collector and...
This circuit was found in a 90s Popular Electronics. It generates tones given by the oscillators and...