v0.26

SMSGGDJ v0.26 — release notes

The headline: YM2413 FM Sound Unit support (SMS only, optional, off by default — it sounds alongside the PSG on the built-in/FM-unit hardware and SMSPlus). A whole second timbral palette.

Added — FM (YM2413)

• FM synthesis — a new FM instrument type plays the chip's 15 ROM patches. Pick a PROG (1–15) and VOL; notes play in tune from a region F-number table. HLD sets note length (F = ring, 1–E = auto key-off). Enable via OPTIONS → FM (persisted).
• FM tables, transpose, and commands — FM instruments honour TBL/TBS tables (volume column re-levels live, pitch column arps), TSP transpose, the X per-note volume command, and a new Y command to set a note's FM program.
• FM drums (FMDRM) — the YM2413's rhythm mode as a kit: one instrument, the note picks the drum (BD/SD/TT/TC/HH, C/C♯/D/D♯/E in any octave). Rides on spare FM voices, so it costs none of the 4 tracks.
• FM custom presets — a PRST field selects one of 8 ROM-baked custom timbres (LEAD, EPNO, SBASS, BELL, BRASS, PAD, PLUCK, SINE) loaded into the YM2413 user patch. (One custom timbre at a time — the chip has a single user patch.)
• FM preset editor (tools/fmpatch.html) — a single-file, offline browser tool to edit the 8 presets (per-operator MUL/AR/DR/SL/RR/KSL/TL, feedback, waveforms, names) and audition them through a JS port of the emu2413 YM2413 core. Download a patched ROM. No toolchain.

Changed

• PHRASE column spacing — NOTE I CMD with room to breathe (SMS + Game Gear).

Fixed

• WAV instruments: HLD is editable again (the cursor was skipping the field).

FM instruments and tracks persist to SRAM like any other; the format stays SMDJ3, fully backward-compatible. SMS save/SRAM hardware-verified; FM-unit and Game Gear hardware still want a check.