Basic Structure
A basic Additive synthesizer such as the one I’m describing has one notable difference- no filter, and no waveform selection. In this design we’re doing all the timbral alteration by selecting the levels of the harmonics. The overall structure is shown below. I’ll break it down stage by stage.
The Harmonic Generator.
The Harmonic Generator container is our fundamental oscillator. This is the pitch that we are using for the note we want to play. Everything else is generated in our Even Harmonics Container and our Odd Harmonics containers.
The Fundamental Oscillator.
This is simple, just an Oscillator HD module, with the waveform preset to Sine wave, pitch input and Audio Output.
Even Harmonics.
These are our 2nd, 4th, 6th, 8th and 10th harmonics so for Standard A at 440 Hz Hz they will be; 880 Hz, 1760 Hz, 2540 Hz, 3520 Hz, and 4400 Hz. We use the same HD Oscillator module again set to a sine wave output. The harmonic frequencies are generated by the offset voltages in the Fixed Values (Volts) module, the voltages are as follows;
2nd Harmonic Osc 1 V
4th Harmonic Osc 2 V
6th Harmonic Osc 2.585 V
8th Harmonic Osc 3 V
10th Harmonic Osc 3.322 V
Odd Harmonics.
These are our 3rd, 5th, 7th, 9th and 11th harmonics so for Standard A at 440 Hz Hz they will be; 1320 Hz, 2200 Hz, 3080 Hz, 3960 Hz, and 4840Hz. We use the same HD Oscillator module again set to a sine wave output. The harmonic frequencies are generated by the offset voltages in the Fixed Values (Volts) module, the voltages are as follows;
2nd Harmonic Osc 1.585 V
4th Harmonic Osc 2.322 V
6th Harmonic Osc 2.807 V
8th Harmonic Osc 3.170 V
10th Harmonic Osc 3.459 V
Controlling the levels of the Partials (Harmonics).
This is just an audio mixer. I have used VCA modules rather than Adjust Level modules for a more natural “feel” to the control over the levels.
The Final stage.
Here we are just using the standard Synth output of a VCA and ADSR module connected up as usual. The waveshaper was something I included to check that I was not getting any unexpected frequencies out of the Harmonic Generator.
Although I haven’t included any other modules such as Waveshapers, filters etc. there’s no reason not to include them and make it more of a hybrid synthesizer.
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