A maker known as RobDevBuilds has built a MOD file optical paper disk player that encodes Amiga tracker music directly onto printed paper, sidestepping the comparatively modest thousand-year lifespan promised by the M-Disk format and keeping the Amiga’s legacy very much alive.
If you heard ‘optical disk’ and assumed a CD full of MOD files, that’s a reasonable first guess, and a MOD-CD player would be a perfectly fine project in its own right. What Rob has actually done is considerably stranger and more ambitious: he’s printing the contents of a MOD file row by row onto paper in a format readable by a custom optical player he’s also building. The result looks, to anyone who’s spent time in a tracker programme, immediately familiar, because that is essentially what it is: the pattern data laid out exactly as you’d see it scrolling past on screen.
How the MOD File Format Makes This Possible
Understanding why this works requires a short detour into what a MOD file actually is. Unlike a WAV or an MP3, which encode audio directly as waveform data, a MOD file works more like MIDI in that it stores a list of notes for playback software to interpret. The playback software is, traditionally, called a tracker, which is where the format’s name comes from. The crucial difference from MIDI is that MOD files are self-contained: the instrument samples are bundled inside the file rather than relying on an external sound module.
MOD files also handle repetition cleverly. Repeating musical sections are stored once as patterns and then referenced by a sequence list, which means the bulk of the data is simply a grid of hexadecimal numbers, one column per voice or instrument, row after row of note events. It’s this structured, text-like nature that makes the format compact enough to have found a second life in keygens, and compact enough to print legibly onto a spinning paper disk.
The front face of Rob’s disk carries all that hexadecimal pattern data, printed using a modified version of the Amiga‘s classic Topaz font. An OCR system reads it back during playback. The rear of the disk is where the self-contained nature of MOD files demands a different approach: the samples themselves need to live somewhere, so Rob encodes the first 1,084 bytes of the MOD file, the instrument samples for each track, the metadata including title and artist, and the pattern sequencing, all in a QR-inspired barcode format he designed specifically for this project.
The Physical Player and Its Current Limitations
Playing back a MOD file optical paper disk requires two cameras, one for each side of the disk, and stepper motors to slide them across the surface in the manner of a linear-tracking turntable. The modest file sizes that define the MOD format mean the 8-bit sound samples can be stored and retrieved without recourse to OPUS compression, preserving fidelity in a way that previous paper-based music storage experiments could not manage.
The player is still a work in progress. Rob has acknowledged that it currently cannot jump between patterns on the disk quickly enough to satisfy the demands of some MOD files, and a follow-up video is in the works to walk through the technical details once those bugs are resolved. Given the hardware involved, a Raspberry Pi is a reasonable inference for the brains of the operation, though Rob hasn’t confirmed the specifics yet.
What’s already working is the core idea: a MOD file optical paper disk that a determined archivist could, in principle, read back with nothing more exotic than a camera and some OCR software. For a format born on the Commodore Amiga in the late 1980s and still very much in active use, that’s a preservation story worth telling.
