FMSound

日本語

A browser-only player and editor for MML played through two FM sound driver engines — PMD (PC-9801) and MUCOM88 (PC-8801). It runs on prebuilt wasm and a shared web UI; no server is required.

▶ https://uraraworks.github.io/FMSound/

No install needed — try it straight in your browser. (Open with PMD / Open with MUCOM88)

What sets this repository apart is that it doesn't just play sound — it draws a FMDSP-style screen that renders each part's playback state (voice, pitch, gate, volume) in real time. The spectrum analyzer and level meters are also driven live from the real driver's output.

Usage

1. Opening the page loads a bundled sample by default (the opening of "Für Elise"). Just press play to hear it.
2. The "Sound driver" dropdown in the header switches between PMD (PC-9801) and MUCOM88 (PC-8801) (also selectable via the ?driver=pmd / ?driver=mucom URL query).
3. The toolbar icons let you "Open a song" (a local .M/.m/.muc file, or drag & drop), "Switch to editor mode" (write and play MML directly), and "Download" (MML source / compiled binary / asm db array — three formats). Opening a file or dropping one also accepts a ZIP/LZH archive (including one holding a .d88 disk image) — the contents are extracted so you can pick a song from inside, same as loading an archive by URL below.
4. Adding ?mml=<URL> opens the page with the MML/song file at that URL already loaded. Pointing it at a ZIP/LZH archive extracts the contents so you can pick a song from inside (loading only — it won't autoplay, since browsers require a user gesture before audio can play, so press play yourself). For a PMD song that needs PCM (one using .PPC/.PZI/.PVI), there's no way to supply a PCM file alongside a standalone song file, so pack the song and its PCM files together into one archive (ZIP/LZH) and point the URL at that (PCM loading follows the same conditions described under "Usage" below). Dropbox share links can be pasted as-is — no need to rewrite them with dl=1; the app rewrites the host automatically (only per-file share links have been verified this way; folder shares and password-protected links haven't been tested). Google Drive links only work through the relay server, so they won't load on a build where no relay server URL is configured (see "Publishing to GitHub Pages" below for how the relay is configured).
5. Keyboard shortcuts: ⌘/Ctrl+Enter to compile & play, Esc to stop.
6. Click a part's row on the FMDSP screen to mute just that part (click again to unmute — there's no solo function). A muted row keeps its original color but dims it, and its keyboard highlight dims the same way. The rhythm part has no row of its own, so mute it by clicking the RHY column in the level meters on the right; the FM1–SSG3/ADPCM columns there mirror the same mute state as their part rows. PMD's PPZ columns (PPZ8, columns 11–18) can be muted the same way too; MUCOM88 has no concept of PPZ8 at all, so this stays unsupported there. Hovering anything mutable (a part row or a level-meter column) draws an outline around it before you click. Parts are shown in three brightness levels — normal, muted (half brightness), and "unused by this song" (quarter brightness, only available when the MML was compiled in this app rather than loaded as an already-compiled .M/.m file). Reloading a song clears all mutes. This only works with mouse/touch clicks; keyboard control isn't supported yet.
7. The "language" button in the header switches the UI between Japanese and English (its label shows the language it will switch to). The choice is remembered in the browser and takes priority over ?lang=ja/?lang=en; without either, it falls back to the browser's language.
8. The header's help icon opens html/help.html, a step-by-step usage guide with screenshots (also available in Japanese/English).
9. The toolbar's "Copy link" button copies a shareable URL for the MML you're currently editing (nothing is uploaded — the song data is packed into the URL's fragment (#s1=...), which browsers never send to a server, so it works on static hosting like GitHub Pages with no server-side storage). Next to the button, a counter (e.g. 2344 / 4000) with a gauge always shows the current link's length; it's tallied when you compile & play (not on every keystroke), reads "not counted yet" while you have unsaved edits, and is recalculated the moment you press the button. If the link would exceed 4,000 characters, the button is disabled and shows exactly how many characters you're over — the limit exists because sites like X don't treat a longer URL as a real link (see net/share-link.js for how this number was measured). If the clipboard copy fails, a read-only text field with the link appears so you can copy it manually. For MUCOM88, if the song uses a disk-specific external voice bank (#voice resolved from a paired system disk rather than written in the MML itself), sharing shows a one-time warning: whoever opens the link won't have that disk, so the instrument sounds will change to the defaults.

What it can't do (important)

The player currently has a few honest limitations worth stating up front.

• It can't load external files referenced by #voice, or by #pcm other than the bundled default bank. #pcm mucompcm.bin (the standard ADPCM bank) is bundled and plays normally; any other #voice filename falls back to default voices. An unresolved #pcm doesn't go silent, though — the standard ADPCM bank stays loaded and plays instead, so the drums (ADPCM) sound different from the original. If a loaded MML references a file that can't be resolved this way, the UI shows a notice (that the voices and drums differ from the original).
• The rhythm part plays through substitute samples that differ from a real YM2608. The bundled sound core doesn't carry the real chip's ROM-derived PCM, so it plays free substitute drum samples instead (html/rhythm/2608_*.WAV; see NOTICE.md for the source; no real chip ROM is used anywhere). The author of the original driver has stated plainly that these substitutes are "fundamentally different in waveform from the real YM2608's rhythm sound," and this project inherits that same caveat. (The UI used to show a notice about this, same as it does for #voice/#pcm, but as of 2026-08-16 it no longer does: rhythm went from "silent" to "audible but different," which is a smaller gap than a completely missing part, so it's no longer called out on every screen. The limitation itself is unchanged.) PMD now plays the same substitute samples too (it used to be silent). PMD's sound core, however, requires rhythm samples in the real chip's fixed-capacity ROM format, so unlike MUCOM88 — which plays the WAV files as-is — the samples had to be trimmed to fit during conversion. So even though both engines share the same source material, the rhythm doesn't sound identical between MUCOM88 and PMD.
• MUCOM88 compile error messages are always in Japanese, regardless of the page's language setting. They come from a Japanese error table built into the wasm module, so even with the UI set to English, the error text itself stays in Japanese.
• The PMD compiler (this project's own MML→binary converter) only supports the v1 basic command set — PPZ8, LFO, portamento, and similar are out of scope. See docs/pmd-compiler-spec.md for details.
• On MUCOM88's K (ADPCM) part, setting the volume command to v255 (the maximum) makes it go nearly silent instead. Volume rises normally up to around v200, but the maximum value v255 drops it sharply — avoid using the maximum.
• The right-pane FMDSP counters CPU POWER COUNT, VOLUME DOWN, and PGM NUMBER can't show a value (shown dimmed instead of a live number). CPU POWER COUNT is permanently unobtainable — browsers have no API for a process/tab's CPU usage. VOLUME DOWN and PGM NUMBER aren't a wasm-export gap: the upstream FMDSP drawing code never had logic to render a value for them, and no data field for either exists in the shared driver interface it reads from. FRAMES PER SECOND, by contrast, is implemented — it just counts the host draw loop's own frequency, no driver data needed. See docs/right-pane-data.md §8 for the source-level detail.
• The rightmost 8 columns of the level meter (PPZ8 1-8) only light up when a PMD song actually uses a PPZ8 bank (.PZI/.PVI, up to two banks). PPZ8 is PMD's 8-channel PCM engine. Loading a song together with its bank file from the same archive (zip, etc.) makes the used channels light up; they stay dark if no bank was supplied, or if the song doesn't use PPZ8 at all. MUCOM88 has no concept of PPZ8 at all, so these columns always stay dark there (unlike PMD, this never changes for MUCOM88). PMD's PPZ columns can be muted and unmuted by clicking, same as the other columns (MUCOM88 still has no support for it, since the concept doesn't exist there). The bar itself keeps moving while muted — the raw meter value isn't affected by the mute mask, same as every other part — and the mute state shows up as dimming instead. See fmdsp/channel-mask.js unusedColumnsFromChannels(), buildPpz8Mask(), and docs/pmd-pcm-support.md for the source-level detail.
• PMD's PCM (.PPC = ADPCM, .PZI/.PVI = PPZ8 banks) only loads when you open the song from the same archive (zip/lzh/etc.) as its PCM files. Dropping a standalone .M/.m file gives no way to supply a PCM file alongside it, so PCM never loads in that case. If a song references PCM that can't be found, the UI shows a notice naming the missing file. .P86 (PMD86) is supported via a JS-side conversion to a synthetic .PPC (see docs/pmd-p86-support.md), while .PPS (PPSDRV) still isn't — the upstream sound core doesn't implement PPSDRV loading, so neither does this web build (if the archive happens to bundle a matching .PPS file anyway, the missing-PCM notice is suppressed to avoid a misleading warning).
• The screen isn't optimized for phones yet, and phone support is planned. Tablets haven't been checked or optimized for at this time.
• Sharing a MUCOM88 song that depends on a disk-specific external voice bank changes its sound for the recipient. The share link (?driver= + #s1=...) only carries the MML text, not the paired system disk's voice.dat; whoever opens it will hear the song with default voices instead. The UI warns about this at share time when it applies (see Usage above).

⚠ MML differences between drivers (t/T/C are swapped)

Between PMD and MUCOM88, the meaning of t and T is reversed. This is a trap that was hit twice during development, so please double-check it.

	t (lowercase)	T (uppercase)
PMD	Tempo (absolute value based on a half note; half the value of a typical BPM)	Raw TimerB value
MUCOM88	Raw TimerB value	Tempo (equivalent to BPM)

In addition, MUCOM88's C is not tempo. It specifies the clock count per whole note (resolution), defaulting to 128. Use T to change the tempo.

Roadmap

• Support for loading #voice/#pcm
• Phone support (both playback and editing)
• Data exchange between apps (e.g. sharing song data)

License and credits

FMSound is provided under CC BY-NC-SA 4.0 (Attribution-NonCommercial-ShareAlike 4.0 International). See LICENSE for the full text.

This isn't a condition chosen by this project — it's inherited because the bundled MUCOM88 carries CC BY-NC-SA 4.0 with a ShareAlike clause, and incorporating it brings FMSound as a whole under the same terms. The PMD side's implementation (98fmplayer) is licensed BSD 2-Clause, so if you want to use just the PMD part under permissive terms, refer to 98fmplayer or the original PMD directly instead of FMSound.

The sound driver implementations are ports of the following upstream projects to wasm. The provenance and full license text for generated artifacts derived from third-party works are collected in NOTICE.md.

• PMD: 98fmplayer (BSD 2-Clause)
• MUCOM88: OPEN MUCOM88 / MUCOM88 on Web (CC BY-NC-SA 4.0 — carries NonCommercial and ShareAlike terms)

The bundled sample song (the opening of "Für Elise," composed by Beethoven, public domain) MML arrangement is this project's own work. See NOTICE.md for details.

No ROM images (PC-98 firmware, etc.) or commercial software data are included in this repository.

Build instructions

This repository does not track upstream/ (the external repositories it references, 79MB) — see .gitignore. As a result, cloning alone won't let you build; fetch them with the steps below.

The fetch locations and pinned revisions are centralized in upstream-revisions.env (the GitHub Actions build also reads this file; see the comments in the file for why revisions are pinned).

set -a; source upstream-revisions.env; set +a

mkdir -p upstream
git clone "$UPSTREAM_98FMPLAYER_REPO" upstream/98fmplayer
git -C upstream/98fmplayer checkout --detach "$UPSTREAM_98FMPLAYER_REV"

git clone "$UPSTREAM_MUCOMWEB_REPO" upstream/MucomWeb
git -C upstream/MucomWeb checkout --detach "$UPSTREAM_MUCOMWEB_REV"
git -C upstream/MucomWeb submodule update --init --recursive

The toolchain is shared via PC98/emsdk (the emscripten SDK), linked in as the emsdk symlink. If the link target is missing, obtain the emscripten SDK separately and repoint emsdk at a valid path.

# Run from the repository root (the directory containing this README.md)

# MUCOM88
cd mucomweb
source ../emsdk/emsdk_env.sh
emcmake cmake -S . -B build-web -DWEB_BROWSER=1 -DCMAKE_BUILD_TYPE=Release && cmake --build build-web -j4

# PMD
cd ../pmdweb
emcmake cmake -S . -B build-web -DCMAKE_BUILD_TYPE=Release && cmake --build build-web -j4

# Assemble both drivers into one directory (for local ?driver= switching checks and to inspect what gets shipped)
cd ..
tools/build_dist.sh

dist/ is the assembled distribution directory (GitHub Pages is expected to serve this). To check it locally, serve dist/ with a static server and open it in a browser (e.g. python3 -m http.server 8000 --directory dist).

The screenshots on the usage page (html/help.html) are generated reproducibly by tools/gen_help_shots.mjs (macOS only — it drives a local Google Chrome headlessly over the DevTools Protocol, no npm dependency added). Run it after tools/build_dist.sh so dist/ is current:

node tools/gen_help_shots.mjs

It serves dist/ on port 8790 and writes html/help/<name>.<lang>.png. There's no need to re-run this unless the screens it captures actually changed.

When mucomweb is configured, patches under mucomweb/patches/ (three of them: exposing accessors, level meters, and the rhythm part's rhythmpath) are automatically applied to upstream/MucomWeb/mucom88. The upstream working tree itself is left unmodified, so no tracking or committing is needed.

Publishing to GitHub Pages (CI)

A push to master runs .github/workflows/pages.yml, which performs the same steps as above (fetch upstream → set up emsdk → build both drivers → generate net/config.js → tools/build_dist.sh) and deploys dist/ to GitHub Pages. The relay server URL is injected from the repository variable DISK_PROXY_URL (Settings → Secrets and variables → Actions → Variables). Build and publishing succeed even if it's unset (the app simply runs without relaying — this default lets forks publish without having to set the variable).

Development notes

The results of analyzing upstream, the reasoning behind design decisions, and driver characteristics discovered through measurement are collected in docs/development-notes.md (Japanese only — useful reference if you're modifying or porting this project).