The Stage 4's envelope amount knobs: a systematic description of their effects

[ns4decode]

This is an informational post. It quantifies the behavior of the Stage 4's two envelope amount knobs: one for the filter, and one for the oscillator.

The statements are numbered in case anybody wants to refer to them in replies. All of these statements are based on my own experiments using the Sync Saw waveform. I'm not affiliated with Nord/Clavia. The Stage 4 is my first synth, so I don't know if this is standard material.

This is for version 1.44 of the OS.

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filter
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Let F be the value of the filter frequency knob, so F ranges from 14 Hz to 32 kHz. Let A be the value of the envelope amount knob, so A ranges from 0 to 10. This is the behavior, in statements numbered F1-F3:

F1. The filter starts at the value F at the beginning of the attack stage, rises to the value F + (32 kHz) * A/10 by the end of the attack stage, and falls back toward the value F during the decay stage.

F2. If A is large enough (say 10), then F + (32 kHz)*A/10 will be greater than 32 kHz. I can't hear frequencies that high, but this still has an audible consequence: it creates a "plateau" where the value remains constant (as far as my ear can tell) until it falls back down to a value whose filtering effect we can actually hear.

F3. If the decay time is infinite, then it remains at the value it had at the end of the attack phase.

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oscillator with env-to-pitch OFF
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Let C be the value of the oscillator control knob, so C ranges from 0 to 10. Let A be the value of the envelope amount knob, so A ranges from -10 to 10. Let |A| be the magnitude (unsigned) of A. This is the behavior, in statements numbered C1-C4:

C1. If A > 0, then the oscillator starts at the value C at the beginning of the attack stage, rises to the value C+A by the end of the attack stage, and falls back toward the value C during the decay stage.

C2. If A < 0, then the oscillator starts at the value C+|A| at the beginning of the attack stage, drops to the value C at the end of the attack stage, and rises back toward the value C+|A| during the decay stage.

C3. If the decay time is infinite, then it remains at the value it had at the end of the attack phase.

C4. The effect of values > 10 is the same as the effect of the value 10 (the "plateau" phenomenon again).

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oscillator with env-to-pitch ON
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Let P be the nominal pitch of whatever key is pressed, and let A be the value of the envelope amount knob, so A ranges from -10 to 10. Let |A| be the magnitude (unsigned) of A. This is the behavior, in statements numbered P1-P4:

P1: If the decay time is finite and A > 0, then the oscillator starts at the pitch P at the beginning of the attack stage, rises to the value P + (4 octaves)*A/10 by the end of the attack stage, and falls back toward the value P during the decay stage.

P2. If the decay time is finite and A < 0, then the oscillator starts at the pitch P at the beginning of the attack stage, drops to the value P - (4 octaves)*|A|/10 at the end of the attack stage, and rises back toward the value P during the decay stage.

P3. If the decay time is infinite and A > 0, then the oscillator starts at the pitch P - (4 octaves)*|A|/10 at the beginning of the attack stage, rises to the value P at the end of the attack stage, and stays there.

P4. If the decay time is infinite and A < 0, then the oscillator starts at the pitch P + (4 octaves)*|A|/10 at the beginning of the attack stage, drops to the value P at the end of the attack stage, and stays there.

A video illustrating the difference in behavior between finite and infinite decay times is posted here: viewtopic.php?t=25955

[WannitBBBad]

Very nice - thanks.