Manual

CRT-4 turns the M-VAVE FM-1 into a four-track groovebox that plays the sound chips of nine game consoles and home computers: the Atari 2600, the Commodore 64, the NES, the PC Engine, the Genesis, the Game Boy, the SNES, the PlayStation and the N64. Pick a console and you play it: its drums on the first track, any of its sixteen sounds on the other three, made the way that console made them, with its own echo or reverb. The whole screen dresses as the console, with a scene of its time that moves with the music. Each console keeps a song of its own: 16-step patterns, chains, chords and punch-in effects, the way LCD-4 works.

1Install

Try it first: the browser emulator runs the same code with sound, played with the mouse, a touch screen or the keyboard.

Install from the browser: open the web installer in Chrome or Edge, connect the FM-1 with a USB data cable and press Install. Don't unplug it while it's writing; when it finishes, the FM-1 restarts into CRT-4.

Install from the command line: download crt4-X.Y.Z.fwsc from the latest release, install Python 3 with pip3 install mido python-rtmidi, and from the CRT-4 source run:

python3 tools/fm1_install.py crt4-X.Y.Z.fwsc

Which version: the Setup page (GLO) shows it at the bottom left, and the start screen under the name.

Go back: "Back to the stock firmware", at the bottom of the installer page, puts M-VAVE's firmware back (download the FM-1 V15 file from the link there, choose it, press the button). M-VAVE's own updater, M-UPGRADE, works too.

Coming from another firmware: CRT-4 keeps its settings where IND-1, LCD-4, AMB-1 and others keep theirs, under its own name, and its nine songs in the FM-1's main store (where some firmwares keep samples). None of them reads the others': CRT-4 starts on the NES with its demo song, and each console's first save replaces what another firmware had saved in that place.

2Getting started

1. Switch the FM-1 on and turn MASTER up. CRT-4 powers on the NES: its start screen, then its demo song, stopped.
2. Press PLAY. Four tracks play: the 2A03's drums, the triangle's bass, pulse arpeggios and a pulse lead with an echo, over a chain of patterns and chords.
3. Hold GLO and turn ALGORITHM. The consoles stand on a shelf; the one you point at comes forward. Let go of GLO: that console powers on, with its own song (its demo, the first time). Press PLAY.
4. Turn ALGORITHM to pick a track. The tabs under the screen show the four tracks and their sounds.
5. Turn PRESETS to give the track another of the console's sounds (on track 1, its other kit).
6. On tracks 2–4, play the keys. OCT− and OCT+ move them an octave. On the 2600, the C64, the NES and the Game Boy a track plays one note at a time: hold several keys on an Arp chords sound and they run as an arpeggio, a note a frame, as the music of those machines did.
7. Turn ALGORITHM to track 1, the drums. A black key picks a part (and plays it); the white keys are its 16 steps: press one to switch it on or off.
8. Press REC (writing) while it plays, and play: what you play goes into the pattern. REC again to stop.
9. Press HOME for the patterns: a white key picks the next one. Hold one and press others: a chain.
10. Hold FX and press a white key: an effect, for as long as you hold it. Hold any button for a second and a card says what it does. Your work saves itself a few seconds after you stop; SAVE saves at once.

3Controls

A page's button pressed again goes back to the Sound page. Hold OCT− and OCT+ together for five seconds for the update mode (see Troubleshooting).

4The consoles

Hold GLO and turn ALGORITHM: the consoles stand on a shelf, the one you point at lifted out and named. Let go of GLO and CRT-4 stops, saves the song you were on, and powers the other console on: its start screen for a couple of seconds, then its song.

Each console keeps its own song: its sixteen patterns, its chains and chords, its tempo, every track's sound and knobs, its kits and its FX page. Going to another console and back finds yours as you left it. The first time you choose a console, its song is its demo; Setup's Demo (hold SAVE) brings the demo back any time.

What changes with the console:

• The sounds: two kits and sixteen sounds of its own, in rows of four: basses, keys, leads, and the sounds that console was known for.
• How they are made: its chip's channels (pulses, triangles, wavetables, FM operators, noise registers), its samples in its own format, its interpolation, its envelopes, rounded as its registers rounded them. See section 13.
• Chords: the 2600, the C64, the NES and the Game Boy play one note at a time on a track; a chord in a step plays as an arpeggio, a note a frame (1/60 s, 1/50 on a PAL machine), as their composers did it. The PC Engine, the Genesis, the SNES, the PlayStation and the N64 play real chords, up to four notes a track.
• The echo or the reverb: the SNES's echo (its delay line and its 8-tap filter), the PlayStation's reverb, the N64's rooms, chorus and flange. The others had none: there, a track's Echo plays its notes again a few steps later and quieter, as trackers did.
• The pan: the 2600, the C64 and the NES were mono; the Genesis and the Game Boy put a channel left, right or both; the others pan anywhere.
• The screen: its colours, its lettering, its scene, its power-on (section 5).

5The screen

The top of the screen is the console's TV (the Game Boy's LCD):

• The status line: the pattern playing (P01), its place in the chain (1/4), the chord (on a tag); then REC, play or stop, and the tempo. A small dot means changes not saved yet. A message takes the middle for a moment when you change something.
• The scene: the console's own, drawn as its games drew (its resolution, its palette, its tricks), with Pip, who lived in LCD-4's LCD, redrawn in each era. The music moves it: the kick, the snare, the bass, the lead's notes and accents.
• The steps: the track's 16 steps. A filled cell has a note (on the drums, the part plays); a tall one is accented; lines across it are a ratchet; a tail joins a slide to the next step; a dot above is a locked knob, a mark at its top-left an effect written there. The bar under it is the playhead.

Below it, in the console's colours: the four tracks (their sounds and meters; a muted one struck through), then the page's name and its four knobs. On the 8- and 16-bit consoles the knobs are level meters in the console's lettering; on the PlayStation and the N64, dials.

6The tracks

Track 1 is the drums; tracks 2, 3 and 4 play the console's sounds. Each track remembers its knobs for every sound, so you can try another sound and come back. Each track has a colour from the console's palette.

The Track page (ENV) sets the track's Level, Pan (as the console could), Echo (or Reverb, Effect: how much of the track goes to the console's effect) and Glide (how long a note takes to slide from the last one). The Mixer (SEL) has the four levels together, and mutes.

7The drums

The black keys pick the part (and play it). The white keys are the part's 16 steps: press a step and let go to switch it on or off. The Sound page's knobs are the part's own: Tune (an octave up or down), Decay (shorter or longer than the part's own), Tone (the part's colour: a noise's rate, a drum's pitch drop, a filter, an operator's level, as the console makes it) and Level.

• ENV + a white key: an accent on that step (all the drums on it play harder).
• EDIT + a white key: the step cleared (every part on it); EDIT + a black key: the part's whole row cleared.
• OCT− / OCT+: the part before, the next part.
• Hold a step and turn KNOB 1 or 2: that step's tune or decay, moved for every part on it.

Every kit has eleven parts on the same keys; most follow the same plan (kick, snare, three toms, a rim or a click, a clap, closed and open hats, a crash, one more), so a pattern written on one kit makes sense on another. The closed hat cuts the open one off. Each console's kits are in section 13.

8Writing

On the steps (any time, playing or not): on the drums, the white keys always are the part's steps. On tracks 2–4, the Steps page (SEQ) turns the white keys into its 16 steps.

• Press an empty step: it takes the notes in hand, what you last played on the keys (a chord, if you played one), one step long. Stopped, you hear it.
• Press a full step: it's cleared.
• Hold a step and turn the knobs: KNOB 1 its note (a chord moves together), KNOB 2 its length (in quarter steps, up to 16 steps), KNOB 3 and 4 the sound's A and B for that step alone (a lock).
• Hold a step and press OCT−: a slide into the next note. OCT+: a ratchet, the note played two, three or four times in its step.
• ENV + a step: an accent. EDIT + a step: cleared.

Live (REC on, playing): what you play goes into the pattern playing, on the nearest step: each key's note and how long you hold it; keys pressed together make a chord on one step (on a mono console it plays as an arpeggio); a key pressed while another is held slides into it. On the drums, the black keys. Knobs A and B turned on the Sound page are written as locks; an effect held is written onto its steps.

Step by step (REC on, stopped, tracks 2–4 on the Sound page): each key (or chord) goes on the next step; EDIT is a rest.

Clearing: EDIT + REC clears the selected track in this pattern.

9Patterns and chains

A pattern holds all four tracks: the drums' steps and accents, the other tracks' steps, the effects written on its steps, and its length. There are sixteen, on the white keys of the Patterns page (HOME), or with HOME held from any page.

• A key: that pattern next (at the end of this one; stopped, at once). The pattern playing is the one you edit.
• Hold a key and press others, or hold HOME and press keys in order: a chain, up to 64 long, repeats allowed. It starts over when this pattern ends.
• SAVE + a key: this pattern copied there. EDIT + a key: that pattern cleared.

The page's knobs: Tempo (40–240), Swing (50 % straight to 75 %), Length (1–16 steps) and Key (everything moved to it).

10Chords

The Chords page (ARP) puts sixteen chords on the white keys, in C (Key moves them):

• A key: that chord, held. Hold a key and press others, or hold ARP and press keys: a chain of up to 64, a chord each time a pattern starts. EDIT + a key: no chords.
• Follow (KNOB 1, for the selected track): the track's notes follow the chord. Write the parts in C; each note moves with the chord's root, and the scale bends to it (in a minor chord E is played as Eb, A as Ab, B as Bb; a seventh flattens B; a suspended chord raises E to F).
• On a mono console, an Arp chords sound given a single note plays the chord that is playing (or the note's own triad) as its arpeggio.

11Effects

Hold FX and press a white key (or use the keys on the FX page): the effect lasts as long as you hold the key. While writing, it's written onto the steps it plays over. EDIT + an effect's key takes it off the pattern's steps.

The FX page's knobs are the console's own (section 13).

12The pages

Setup: Tune ±50 cents; MIDI out off or on; Clock Auto (follows MIDI clock when it comes) or Internal; Demo: the console's demo song, back when you hold SAVE (it replaces this console's song; the other consoles' are not touched). The status line shows the load (CPU).

13The nine consoles, one by one

Each console's sounds are listed in their rows: the basses, the keys, the leads, then its own. Made of says which part of the chip (or which kind of sample) makes the sound. Knobs A and B can be locked on a step. Wave, Duty, Shape and the like are switches: a few positions, a detent each.

Atari 2600 (1977)

The TIA: two channels, each a 5-bit frequency divider (the 31.4 kHz audio clock divided by 1 to 32), a waveform (sixteen settings made of more dividers and of 4-, 5- and 9-bit polynomial counters) and a 4-bit volume. A note becomes the divider nearest to it, so the 2600 plays near the notes, rarely on them: that is its sound. Organ and Chime use both channels at once.

FX page: Echo (the trackers' echo: how many sixteenths later), Repeats, Region (NTSC or PAL: the clock a little slower, 50 frames a second), TV (how much of a TV's little speaker you hear).

Commodore 64 (1982)

The SID (6581): three voices of four waveforms (triangle, saw, pulse of any width, noise) that can be combined, ring-modulated or hard-synced by another oscillator, under the SID's ADSR (a linear attack, a decay and release that slow as they fall, sixteen sustain levels), through its multimode filter. Its music ran at 50 frames a second: arpeggios a frame a note, pulse widths and filters swept a frame at a time, drums made by changing the waveform from one frame to the next. The Digi kit and the voice play 4-bit samples through the volume register.

FX page: Echo, Repeats, Chip (the 6581 or the 8580: another filter curve, cleaner; and its digis much quieter, as they were), TV.

NES (1983)

The 2A03 (two pulses of four duties with an 11-bit period, the 32-step triangle that has no volume, the noise register at sixteen rates, the 1-bit DMC) and the Famicom's expansion chips: the VRC6 (pulses of eight duties, a seven-step sawtooth that folds over when driven), the FDS (a 64-step wavetable, its modulator, its low-pass), the N163 (4-bit wavetables), the 5B (its envelope run as a buzzing waveform). The NES's mix and output: mono, non-linear DACs, the Famicom's filters.

FX page: Echo, Repeats, Region (NTSC or PAL), TV.

PC Engine (1987)

The HuC6280: six channels, each a 32-step table of 5-bit values written by the game, a 12-bit period, a 5-bit volume in 1.5 dB steps and its own left and right; noise; the LFO (one channel bending another's pitch: a vibrato, or at audio rate something near FM); DDA (5-bit samples written by hand). The CD-ROM's ADPCM (an OKI MSM5205) plays the CD sounds.

FX page: Echo, Repeats, Stereo (the PC Engine's stereo, or the TurboGrafx's mono), TV.

Genesis (1988)

The YM2612: four operators a voice in eight algorithms, the first fed back into itself; each operator its multiple, detune, level and envelope (attack, two decays, sustain, release, scaled by the key). Its output goes through a 9-bit DAC with a step at zero (the "ladder": quiet notes grow gritty). Channel 3 can give each operator its own frequency (Ch3 bells). The SN76489: three squares and a noise in 2 dB steps. The DAC kit and the voices are samples played through channel 6, as 4-bit deltas.

FX page: Echo, Repeats, Model (the Model 1's warm low-pass and its ladder, or the Model 2's clean output), TV.

Game Boy (1989)

Four channels: two pulses (the first with a sweep), the wave channel (32 steps of 4 bits, written by the game, with only four volumes, so it steps rather than fades: the trackers' wave synths and speech rewrote it as it played; the wave kit plays 4-bit drums through it), and the noise (15-bit, or 7-bit and metallic). Each channel goes left, right or both. The output has a high-pass and, on the first model, a soft top.

FX page: Echo, Repeats, Model (DMG, Pocket, Color: their filters), Speaker (the Game Boy's own little speaker instead of headphones).

SNES (1990)

The S-DSP: samples in BRR (16 samples in 9 bytes), at 32 kHz, through its 4-point Gaussian interpolation (the soft top that is the SNES's sound), under its ADSR stepped by its rate table (and GAIN for releases); no more than two octaves over a sample's root. 64 KiB of sound memory held a game's samples: CRT-4's SNES bank is that size, its samples short, their loops tight.

FX page: Delay (the echo's: 16 to 240 ms), Feedback, Filter (the echo's 8-tap filter: flat, soft, dark, bright), Echo (how loud). The Track page's Echo is each track's share of it.

PlayStation (1994)

The SPU: samples in its ADPCM (28 samples in 16 bytes), at 44.1 kHz, the same Gaussian interpolation, its exponential envelope; and its reverb: reflections, combs and allpasses at 22 kHz, with presets after its kinds (CRT-4's own settings). The Jungle kit is one breakbeat cut in eleven slices, a slice a black key.

FX page: Reverb (Room, Studio S, M and L, Hall, Half echo, Space echo, Chaos, Delay), Depth, Feedback, Tone. The Track page's Reverb is each track's share of it.

N64 (1996)

Its audio: samples in its ADPCM kind (16 samples in 9 bytes, each sample with its own predictors), mixed at 22 kHz (or 32), a cubic between samples, the audio library's straight-line envelopes; an octave over a sample's root at most. Its effects: a small and a big room, an echo, a chorus, a flange.

FX page: Effect (Room, Big room, Echo, Chorus, Flange), Amount, Feedback, Rate (22 or 32 kHz: the mix's rate, its top end with it). The Track page's Effect is each track's share of it.

About the samples: none are recordings. Every sample (the drums, the strings, the voices, the breakbeat) is made by a program in the CRT-4 source (tools/bank), by modelling the instrument, then put in the console's own format at its own rate, so the format's artifacts are the console's.

14MIDI

MIDI comes in over USB and the TRS jack, and goes out over USB.

• In, notes: channel 1 (or 10) plays the drums (General MIDI: kick 36, snare 38, toms 41, 45 and 48, rim 37, clap 39, closed hat 42, open hat 46, crash 49, the eleventh part 56); channels 2, 3 and 4 play tracks 2, 3 and 4. While writing and playing, they're written like the keys.
• In, clock (Clock: Auto): the steps follow MIDI clock; start and stop start and stop CRT-4. The status line shows EXT for the tempo.
• Out (MIDI out on): the drums on channel 10, tracks 2–4 on channels 2–4; and clock with start and stop when CRT-4 runs on its own tempo.

15Saving

CRT-4 keeps everything in the FM-1's memory: the console in use, the setup, and each console's song (its patterns, chains, chords, every track's sound and knobs, the kits).

• By itself: a few seconds after a change, but only while stopped. Writing to the memory interrupts the sound for a moment, so it never happens while it plays. A dot in the status line means there are unsaved changes.
• SAVE: saves now, playing or not.
• Another console: the song you leave is saved first.

16Troubleshooting

Update mode: hold OCT− and OCT+ together for five seconds. A countdown appears; let go before it ends to cancel.

Calibration: if a button or knob does the wrong thing, hold OCT− and OCT+ while you switch the FM-1 on. The screen then asks you to press each button and turn each knob in turn.

Clicks or dropouts: the most CRT-4 can be asked for is three tracks of four-note chords with every drum on every step, on the Genesis (four operators a note). If the FM-1 ever runs short, CRT-4 plays fewer notes at once on a track (three, then two) until it has time again. The Setup page shows the load.

After a crash: CRT-4 shows a red CRASH screen and restarts by itself a few seconds later. The next start shows RESTARTED AFTER A CRASH and an address (PC ...) for a moment. If you report the problem, include that address and what you were doing.

Safe mode: if CRT-4 crashes twice in a row while starting, it starts in SAFE MODE instead. There's no sound, but USB works, so the web installer can reach it: reinstall CRT-4, or put the stock firmware back from the same page. Press PLAY to try starting CRT-4 normally again. If even safe mode fails twice, the FM-1 drops into the chip's own update mode, and only the rescue below can reach it.

Recovering an FM-1 that won't start

An FM-1 in the chip's own update mode shows a blank screen, and neither the web installer nor M-VAVE's updater can see it. A script in the CRT-4 source puts M-VAVE's firmware back, on a Mac, with the USB cable you already have. In Terminal, from the CRT-4 folder:

bash tools/fm1_rescue.sh

1. If a window asks to install the command line developer tools, click Install. When it has finished, run the line again.
2. If it asks for a password, type your Mac password (nothing shows as you type) and press Return.
3. When it says it's waiting, plug the FM-1 in and switch it on. The script catches it, checks the chip, saves a backup of the FM-1's memory in the fm1-rescue folder in your home folder, and asks before it writes anything.
4. Type yes and press Return. Don't unplug anything until it says it's restarting the FM-1. The FM-1 then starts into its original firmware, and you can install CRT-4 again from there.

The script downloads M-VAVE's FM-1 V15 firmware and JieLi's flash loader, and checks both against known fingerprints. It writes only the firmware area of the memory, never the bootloader or the FM-1's own settings, and checks everything it writes. Running it again is always safe. If the FM-1 never shows up at all, Felucca's FM-1-transporter (a small RP2040 board wired to the USB lines) can still reach it.

17Credits

CRT-4 is free software under the GNU General Public License, version 3. If you share the firmware, you must also share its source code.

• CRT-4's sounds are modelled on the sound chips of the Atari 2600 (TIA), the Commodore 64 (SID 6581 and 8580), the NES and Famicom (2A03, VRC6, FDS, N163, 5B), the PC Engine (HuC6280, the CD-ROM's MSM5205), the Genesis (YM2612, SN76489), the Game Boy, the SNES (S-DSP), the PlayStation (SPU) and the N64, from their public documentation. Its samples, music, scenes, characters and presets are its own: no recordings, no game's music or graphics, no console maker's software or data.
• CRT-4 is built on LCD-4, itself built on IND-1 and on AMB-1 by Charles Vestal: the engine's frame, the sequencer, the screen and knob code, the simulator and the browser emulator.
• The platform (hardware layer, USB, update loader, installer and storage) is from Felucca by Leo Kuroshita, Hügelton Instruments, by way of X0X, AMB-1, IND-1 and LCD-4. X0X's drum machines showed how the black keys pick the parts.
• The idea of running FM-1 firmware in the browser comes from Groove OS.
• The fonts are Barlow Semi Condensed (SIL Open Font License) and CRT-4's own pixel font.

M-VAVE and FM-1 are trademarks of their owners, as are the names of the consoles, computers and chips above (Atari, Commodore, Nintendo, NES, Famicom, Game Boy, SNES, Super Famicom, N64, NEC, PC Engine, TurboGrafx, Hudson, Sega, Genesis, Mega Drive, Sony, PlayStation, Yamaha, Konami, Namco, Sunsoft, OKI). CRT-4 is not connected with any of them, nor with Hügelton Instruments; their names are used only to say what each sound is modelled on.