Changing filter envelope slope shape (convex vs concave) via modulation matrix produces distinct filter sweep characters

Most synthesisers offer only a linear ADSR envelope. A more advanced technique uses the synth’s modulation matrix to modulate the filter envelope’s own attack or decay time parameter with the envelope amount — positive modulation creates a convex slope (fast start, slow finish); negative modulation creates a concave slope (slow start, fast finish). The result is a filter sweep with a noticeably different movement quality compared to linear. This technique is only possible on synths with a capable modulation matrix and is a sound-design tool for creating more organic or idiosyncratic filter movement.

Examples

Tip 11: ‘try using different slope types if your synth supports them. If it doesn’t, you may be able to force it to if it has a capable modulation matrix. This can be done by using the filter envelope amount to modulate the attack or decay time - positive modulation creates a convex slope, negative modulation a concave one.‘

Assessment

In a synth with a modulation matrix, create a filter sweep with a linear envelope. Then route the envelope amount to modulate the decay time positively and then negatively. Describe how the sweep shape changes in each case and which sounds more natural vs mechanical.