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docs/pitch_envelope.md

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+# Pitch Envelope
+
+Control pitch modulation over time with a dedicated ADSR envelope.
+
+## Envelope Amount
+
+```forth
+"bass" s 0.5 penv .   ( pitch envelope depth )
+"bass" s -0.5 penv .  ( negative envelope )
+```
+
+## Envelope Shape
+
+```forth
+"kick" s
+  1.0 penv     ( full envelope depth )
+  0.001 patt   ( instant attack )
+  0.1 pdec     ( fast decay )
+  0 psus       ( no sustain )
+  0.1 prel     ( short release )
+.
+```
+
+## Classic Kick Drum
+
+```forth
+"sine" s
+  40 note
+  2.0 penv
+  0.001 patt
+  0.05 pdec
+  0 psus
+.
+```
+
+## Words
+
+| Word | Stack | Description |
+|------|-------|-------------|
+| `penv` | (f --) | Set pitch envelope amount |
+| `patt` | (f --) | Set pitch attack time |
+| `pdec` | (f --) | Set pitch decay time |
+| `psus` | (f --) | Set pitch sustain level |
+| `prel` | (f --) | Set pitch release time |