In this simple project, we are going to make a melody generator circuit using the IC UM66. This IC (UM66) has an inbuilt beat and tone generator. It has three legs like a transistor. This IC (UM66) has many versions with different sounds. This circuit is very useful for basic hobby students.

Melody Generator Circuit using IC UM66

Melody Generator Circuit Description

The  UM….. series are designed for use in calling bells, cell phones, and toys. It has built-in ROM programs for music. This device has very low power consumption.  The melody is generated at pin 3 of UM66 IC and here it is amplified by using a transistor (T1) to drive the speaker. This can generate music without transistors but the voice will b very low. Resistor R1 limits the base current of T1 within the safe values. Capacitor (C1) is meant for noise suppression.



When using this simple melody generator circuit following things must be in mind.

  • Do not exceed 4.5 V. Power supply must be between 1.5V & 4.5V.
  • For loud melodies, Speaker can be driven with an external NPN  transistor.
  • The melody begins from the first if the power is reset.
  • For better result circuit should be on a good quality common board.
  • Melody can be generated without a transistor.


  • Capacitor 1uF 16v
  • UM66 IC
  • Speaker /buzzer
  • Resistor 4.7k
  • Power supply – 1.5-4.5V DC
  • BC 547  or any NPN transistor

Circuit Diagram without Transistor

The circuit can be used without any extra transistors. Music can be generated using the ic. Anyhow, the transistor is used to make a melody in loud voice. The circuit  Diagram without any transistor is given below.

Circuit Diagram without Transistor

Circuit Diagram of Melody Generator Circuit

In this circuit, we have used an extra transistor and a commonly used transistor.

Circuit Diagram of Melody Generator Circuit

Working Of Melody Generator Circuit

The working of the circuit is very simple. We have used UM66 a Happy Birthday Tone Generator IC in the circuit and you can change it with any other ICS in the given below list. The operating voltage of the circuit is around 1.5 to 4.5v DC, so We have used a 3v battery to power the circuit given above.

The output of this IC was then fed into the base of the transistor BC547 to drive the speaker connected to the collector of the TransistorT1. Here a Transistor BC547 works fine and an R1 4.7k  resistor is used to limit the current to the base of the transistor T1.


The UM66TXX series is designed specifically for generating melody, and tone generation circuits. It consists of a chip ROM programmed with a particular tone. The IC UM66TXX consumes low power since it was produced by CMOS technology. The last two digits of ic specified tone/ melody. The list of some common tone generator IC and their equivalent numbers.

  • UM66T01 – Jingle bells, Santa is coming to town, and We wish you a merry Xmas
  • UM66T02 – Jingle Bells
  • UM66T04 – Jingle Bells, Rudolph the red-nosed reindeer, and  Joy to the world
  • UM66T05 – Home sweet home (a nice melody)
  • UM66T06 – Let me call you Sweetheart
  • UM66T08 – Happy Birthday 2 you
  • UM66T09 – Wedding march
  • UM66T11 – Love Me Tender and Love me True
  • UM66T13 – Easter Paradise
  • UM66T19 – For Elise
  • UM66T32 – Waltz
  • UM66T33 – Mary Had a little Lamb
  • UM66T34 – The train is running fast
  • UM66T68 – It is a small world

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