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This neat little circuit can play 8 note tunes at any speed you want. You select the notes with 8 trim pots. The speed in selected through a ninth pot. The circuit draws very little power and can be powered by a 9 volt battery, with the addition of a 7805 regulator to power the TTL logic used.
| R1 | 1 | 10K Trim Pot | |
| R2 | 1 | 1K 1/4 W Resistor | |
| R3, R4, R5, R6, R7, R8, R9, R10 | 8 | 500 Ohm Trim Pot | |
| C1, C3 | 2 | 10uF 12V Electrolytic Capacitor | |
| C2 | 1 | 1uF 12V Electrolytic Capacitor | |
| U1 | 1 | 555 Timer | |
| U2 | 1 | 7490 Binary Counter | 74LS90, 74HC90 |
| U3 | 1 | 7445 BCD To Decimal Decoder | 74LS45, 74HC45 |
| U4, U6 | 2 | 7404 Hex Inverter | 74LS04, 74HC04 |
| U5, U7 | 2 | 4016 Quad Bilateral Switch | |
| U8 | 1 | 3909 LED Flasher/Oscillator | |
| SPKR1 | 1 | 8 Ohm 500mW Speaker | |
| MISC | 1 | Board, Wire, IC Sockets |
1. R1 controls the speed at which the notes are played. R3-R10 control the pitch of those notes.
2. The circuit will operate fine on a 9V battery, with the addition of a 7805 regulator to power the TTL logic used.