The Additive Lowpass
Additive synthesizers can tend to be bright.
Sine Machine does a lot behind the scenes to avoid creating a piercing mess of high frequencies. But is a synth a synth without a lowpass?
There are two parameters, Filter Cutoff (x axis) and Filter Slope (y axis).
The Filter Cutoff tells the engine “when a harmonic is above this frequency, make it quieter”
The Filter Slope is how fast harmonics above the cutoff will trend towards 0 volume. It ranges from 0 to 64db.
Traditional synth filters vs. Sine Machine’s “additive filter”
Traditional lowpass filters tend to be fixed in how fast they attenuate frequencies. For example, the Moog 4-pole (4th order) lowpass attenuates at 48db per octave. There’s often one VCF that all voices feed through after the oscillators.
Sine Machine’s filters operate on the harmonic volumes before they are fed into the oscillators. You can apply gain reduction variably, smoothly interpolating between 0db/per octave reduction and brick wall 64db per octave reduction.
You can think of Sine Machine’s lowpass as more like an EQ in terms of its flexibility.
When working with subtractive/wavetable synthesizers, you might key-track the lowpass’s cutoff to let in more high frequencies when you play note higher on the keyboard. In an additive synth, you’d just turn down the higher harmonic volumes to get the same effect. That’s the default out of the box for an additive synthesizer, no lowpass needed.
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