diff --git a/doc/4-instrument/standard.md b/doc/4-instrument/standard.md
index 2da6e1601..112723569 100644
--- a/doc/4-instrument/standard.md
+++ b/doc/4-instrument/standard.md
@@ -2,9 +2,17 @@
 
 The instrument editor for NES and PSG (SMS, MSX, and such) consists of these macros:
 
-- **Volume**: volume
-- **Arpeggio**: pitch in half-steps
-- **Duty**: duty cycle and noise mode for NES channels. _Note:_ This has no effect on Sega Master System.
-- **Panning**: output for left and right channels
-- **Pitch**: fine pitch
-- **Phase Reset**: trigger restart of waveform
\ No newline at end of file
+- **Volume**: volume.
+- **Arpeggio**: pitch in half-steps.
+- **Duty**: duty cycle and noise mode.
+  - NES noise modes:
+    - `0`: long noise.
+    - `1`: short noise.
+  - PSG noise modes:
+    - `0`: short noise, preset frequencies.
+    - `1`: long noise, preset frequencies.
+    - `2`: short noise, use channel 3 for frequency.
+    - `3`: long noise, use channel 3 for frequency.
+- **Panning**: output for left and right channels.
+- **Pitch**: fine pitch.
+- **Phase Reset**: trigger restart of waveform.
\ No newline at end of file