The AHDSR module provides an envelope generator with Attack, Hold, Decay, Sustain, and Release stages. As pictured above, the A, H, D, and R stages have settable times, while the S stage has a settable level (which is maintained until a Note Off occurs). This is a fairly standard type of modulator, although the implementation in Alchemy is more versatile than most.

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A description of each control follows.

• Current AHDSR field. Alchemy provides up to 16 AHDSRs (one by default, more if you create them when assigning modulators — see the Modulation page of this Manual for details). You can access each AHDSR’s control panel by selecting its number in the Current AHDSR field.

• FILE. Clicking the FILE button opens a pop-up menu from which envelope presets can be loaded or saved to files (*.ahd). A collection of useful presets is included (in the ‘Libraries’ folder within Alchemy’s data directory). You can also ‘Copy’ and ‘Paste’ settings between AHDSR modules, or choose ‘Clear’ to initialise the module.

• TRIGGER. When the TRIGGER button is activated, the envelope re-triggers (starts again from the beginning) with each new note. With TRIGGER deactivated, the envelope is effectively monophonic (i.e. it triggers on the first note and persists for subsequent notes in the same legato phrase).

• Attack. Controls the envelope’s ‘attack’ time, i.e. the time taken to reach peak amplitude after a note is played. From 0.00 seconds to 20.00 seconds.

• Hold. Controls how long peak amplitude is held before the ‘decay’ stage of the envelope begins. From 0.00 seconds to 20.00 seconds.

• Decay. Controls the envelope’s ‘decay’ time, i.e. the time taken for the amplitude to ramp down to the ‘sustain’ level. From 0.00 seconds to 20.00 seconds.

• Sustain. Sets the envelope’s sustain level, as a percentage of peak amplitude (adjustable from 0% to 100%).

• Release. Controls the envelope’s ‘release’ time, i.e. the time taken for signal amplitude to ramp back down to zero. From 0.00 seconds to 20.00 seconds.

Envelope shaping

The Attack, Decay and Release controls each have an associated set of switches, giving you a choice of shapes for each of these stages. There are a linear shape; two convex shapes, with different degrees of steepness; and two concave shapes, again with different degrees of steepness. The different shapes produce characteristically different effects.