Iseq (Steve Judd's C64 music editor, 2002) cheat sheet
From Iseq (Steve Judd's C64 music editor, 2002) · print · built 2026-08-31
Reference
Cheat sheet#
Everything from the posts and screenshots in s-sidin01-iseq; the full key list on the help screen is only partly legible there.
| key / value | meaning |
|---|---|
ctrl-h | help, on every screen |
f1 | edit tune |
ctrl-x / ctrl-c / ctrl-p | cut / copy / paste |
shift-t | transpose |
ctrl-t | tempo (CIA timer) values |
ctrl-a | arpeggio editor (from the instrument editor) |
shift-clear | clear tune; detects PAL/NTSC and sets the default timer |
cbm + / cbm - | double / halve playback speed |
$4cc7 | first tempo value for a PAL frame ("behave just like a VIC interrupt") |
$42c6 | NTSC frame |
$417f | old NTSC with the R56A VIC (64 cycles per line) |
JSR $1003 | play call; SYS 4102 plays a tune from BASIC |
Instrument fields (the editor's names): d415 d416 d417 d418 (filter and volume registers), atdk attack/decay, surl sustain/release, pwid pulse-width list, freq fixed-frequency list, creg control-register list, frq+ frequency-add list, fixf restore the note's frequency, gate gate/control byte.
Tune notation (as printed for the Commando cover): voice rows of pattern letters with trans=n (semitones, negative allowed), gate=n, hard+; patterns of inst=n(name), dur=1(6) / dur=3(12), arp=n, gate+ / gate-, notes a1 h a1 a2 (h = hold), rest (orderlist).
Recipes from Judd: vibrato frq+ 0100 0200 0100 0000 ff00 fe00 ff00 0000 looped ("not proportional"); drum = call 1 waveform $81 at frequency $a000, call 2 $11 at $a000, call 3 $41 at the note's frequency with fixf (wavetable-programming).
Techniques
Vibrato and delayed vibrato › Iseq (2002): vibrato as an additive list #
Steve Judd's iseq has no vibrato command; an instrument's frq+ list is added to the current frequency on every player call, so a vibrato is frq+ 0100 0200 0100 0000 ff00 fe00 ff00 0000 looped — Judd's own example, with the caveat that it is "not 'proportional' — you wouldn't use the same modulations at low and high frequencies" and the upside that one list can also carry a rising frequency, an ornament or an "asymmetric" vibrato. His Commando lead uses frq+=0000 0040 0080 00c0 00c0 0080 (source: s-sidin01-iseq).
- Why Galway's middle phase is twice as long: Tognon's figure for the Arkanoid vibrato (
+$14 × 3, −$14 × 6, +$14 × 3after$1Ecycles) shows the first phase climbing from the note's pitch to the top, the double-length second phase crossing to the bottom, the third returning to the centre — "necessary for having the correct up/down sequence" — before flag$05restarts the phases from the current frequency (source: s-sidin04-galway-arkanoid).
Wavetable programming (waveform / arp tables) › Iseq (2002): the three-call drum #
Judd's description of a drum in his register-level editor iseq is the recipe every table player encodes: "1st player call: waveform=$81 freq=$a000 (or whatever); 2nd player call: waveform=$11 freq=$a000; 3rd player call: waveform=$41 freq=original value" — the instrument's fixf "restores the frequency, that's all". His Commando crash is two calls of noise at $0F82 then $1F04 with control $81, $80; crish-v1 runs creg=15 81 81 15 — triangle + ring modulation, noise, noise, back (source: s-sidin01-iseq).