Modulo Melody

[synaesthesia]

Based on the design of the 16-tone divider from another thread, I built this simple Melody/Pattern Generator using only two chips. It works like this: a base frequency is generated by the 4060 and sent to the first divider U1A. The levels at D10,D11,D12 determine the division between 8 and 15. This results in eight possible (microtonal) notes. The output is mixed by a resistor network from Q1 and Q2.

The current division is determined by a second counter U1B which is stable most of the time. At regular intervals a pulse from a low division (Q9) of the 4060 enables the second counter for a brief moment and during that counts the number of pulses coming directly from the 4060 clock generator at pin 9. During that moment the first counter is disabled. For the video I have added a red LED on the right hand side that flashes briefly at that moment.

After the pulse length determined by C2/VR2 passed, U1A continues to run, and the new division is set by the new counter status of U1B. The latter depends on the previous counter state, the number of clock pulses arriving at U1B combined with the divider setting from the levels at D1,D2,D3. When changing the setting of VR2, the length of the pulse that enables U1B will change and thus the number of clock signals that determine the next tone. While VR2 is stable, U1B acts as a modulo counter, so the melody will repeat itself after a certain number of tones. The second counter is wired as a variable divider as well to maximize the length of the melody sequence.

Because I am using the 4060 to generate the base frequency as well as the tempo, I added a switch to select between low and high tempo rates. There is room for even more variation of the generated melodies if the input to the anodes of D1,D2,D3 are made switchable between the 4060 counter outputs, or HIGH or LOW logic levels. When used as a pattern generator, the pattern output is available at Q0,Q1,Q2 of U1B. For the video I have added three LEDs to show the current state of these three outputs.

Sorry for not uploading a sound file. After the last driver update my laptop decided to stop recording via the audio combo-jack.

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[Steveg]

I was having trouble working out how the circuit operated until I remembered that the 4520 has the odd arrangement where either of the Clock or Enable inputs can be used as the clock as long as the other is held at the correct voltage. Clever design Synaesthesia!