This simple circuit can provide hours of enjoyment as you learn tunes, play duets or just make some really weird sounds by pushing all the buttons at once. You have probably seen this ciruit before, it is fairly common. I have seen it in several books. The best thing about the circuit is that you can tune each individual note, or go to a whole new octive by changing one capacitor (C1). Because of this, it is possible to from an entire Transistor Organ ensemble. Why you would want to do this is anyone's guess...
Part Total Qty. Description Substitutions R1-R8 8 250K Trim Or Regular Pot R9, R12 2 100 Ohm 1/4 W Resistor R10 1 10K 1/4 W Resistor R11 1 220 Ohm 1/4 W Resistor R13 1 5K Pot C1 1 0.01uF Capacitor C2 1 0.1uF Capacitor Q1 1 2N4891 Unijunction Transistor Q2 1 2N2222 Transistor 2N3904 S1-S8 8 SPST Switch SPKR 1 8 Ohm 2 W Speaker MISC 1 Wire, Circuit Board, Knobs For Pots
1. You can tune the organ to any instrument by adjusting R1-R8. I used a clarinet to tune mine, but you can of course use any instrument you wish.
2. The circuit may drain a 9V battery fairly quickly at full volume. You may remove R11 for even more sound.
3. You can rig up a relay and a foot switch to change C1 (for a different octive) while your playing.