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2. Artificially ageing oscillators
1 Now that we know what our favourite ancient oscillator waves look like, we can use that knowledge to better simulate them in software. We’ve got a number of options, but let’s dive into the deep end by building a vintage-style waveform from the ground up. To do this, we’re going to call upon KarmaFX Synth, a mighty modular with an additive oscillator. 2 We’ll start from scratch by opening the Bank menu in the bottom and choosing New Bank. We’ll name it after which we get a clean slate. Right-clicking on the Output module’s title bar allows us to choose a new Controller module as an Input. The default Controller is Note Pitch – just what we need. Click the Controller’s title bar to add an Amplifier as input. 3 Next, we’ll add an Additive Generator as the input to the Amplifier module. Choosing a square wave (from the Waveform menu), we’ll click the middle button in the upper-right, next to the display. This shows the individual harmonics in our square waveform. Reduce the value of the Monics knob to around 70, as indicated in the green waveform display. 4 The display shows the amplitude of every harmonic. Only odd harmonics are present in an ideal square wave, so there are gaps between each odd harmonic where the even ones would normally appear. But imperfect vintage square waves have low-level even harmonics, too. Let’s draw them in with the mouse, as above. 5 Let’s keep fine-tuning our harmonics, all the while watching our oscilloscope image. We’ve opened an instance of s(m)exoscope for a better view. As you can see, we can achieve something with similarities to the square waves produced by our vintage Korg MS-20, sharing some characteristics with the square waves produced by the Prophet-5 and VCS3. 6 Let’s go back to the ‘perfect’ square wave. Now we’ll add a pair of filters to our signal – one high-pass, the other lowpass. We’ll nudge the Cutoff of the highpass up just slightly. Next, we’ll decrease the low-pass filter’s Cutoff to 9.1 kHz and boost the Resonance. In doing so, we get some – but not all – of the characteristics of the vintage square wave.