Here is the circuit diagram of a simple yet interesting mini organ based on UJT 2N 4891 (Q1). You can produce the desired sound by pressing each pushbuttons. You have also the option to set each push button to produce the desired tune you want.

The circuit is based on a UJT oscillator who’s frequency is determined by the Presets R6 to R13 (one at a time) and capacitor C2. The transistor Q2 drives the speaker to produce reasonable sound output. For each pushbutton press the corresponding preset will be added to the circuit, and the UJT oscillates in a frequency proportional to it. This frequency will be amplified by the transistor to produce the sound at the speakers. A 9V battery or 9V DC power supply can be used to power the circuit.

Circuit diagram with Parts list.

UJT Organ Circuit
UJT Organ Circuit


  • Power up the circuit and adjust the presets (R6 to R 13) to get the desired tune at the  output for the press of corresponding push button.
  • Preset R1 (5K)  can be used as a volume control.
  • You can also try different values for C2 get the desired tunes.
  • All capacitors are of ceramic type.


  1. asif ali pv

    anyone please name a component can be used in this circuit instead of ujt 2n 4891

  2. Hi, can someone please show a new diagram that will work? or can anyone tried this diagram please share the problems and solutions. is this working please help. please send me a block diagram and flow chart of this project. thanks. 🙂

  3. seetharaman

    Hi Gauri Shankar yes your are correct R2 should be 100K and R3 should be left, as it is the current limitter for the trasistor. If you want higher volume use LM386 or TBA820 modules available in the market which are suitable for 9volt supply and 8 ohms load.

  4. gauri shankar

    the fixed biasing circuit used to amplify the out put from the ujt is not good enough. there is biasing problem wid it . i used a potential divider circuit, it worked really great.
    ujt2n2646 works for the circuit. try removing the resistor connected to the collector for louder sound.