Amp Envelope

Katla features five amp envelopes with shared controls for attack, decay, sustain, and release. You can offset their timing with the key-tracking knob, creating timing differences across the keyboard. Turning the knob clockwise speeds up envelope times for higher notes, while turning it counter-clockwise gives lower notes the faster envelopes.

Looping

The amp envelopes can be looped by pressing the Loop button. When looping is active, the envelope cycles once it reaches the end of the attack and decay stages. Increasing the sustain value shortens both the attack and decay stages, resulting in a faster loop and also affecting the modulation depth. If you release a note before it has completed its decay stage, the envelope will move into the release stage.

When looping with the attack, decay and sustain set to their lowest positions, the envelope oscillates at C1 (32.7 Hz). This makes audio-rate amplitude modulation (AM) possible, tuned to each note by using the key-tracking knob.

At the opposite extreme, when the release is set to its maximum value, the envelope’s release time is approximately one hour.

Tip

One interesting way to explore the Amp Envelope is by engaging Katla’s Skriða parameter, which randomizes envelope times on every note trigger. Send an arpeggiated sequence into Katla, set the decay shorter than the note length, apply a moderate release, and dial in some Skriða.

This causes the decay time to change from note to note, making some notes enter the release phase while others do not, resulting in dramatic variations in note length. Combine this with looping and key-tracking for an even more animated and evolving result.