Convert MOD to AMR — Free Online Converter

The MOD format emerged from the Commodore Amiga demo scene in 1987, where programmers and musicians collaborated to create impressive audiovisual displays within severe hardware constraints. MOD files achieve their remarkable compactness by storing short 8-bit instrument samples alongside pattern-based sequencing data — the playback engine reads note events from a grid, fetches the corresponding sample, pitches it to the correct frequency, and mixes up to 4 channels (or more in extended trackers) into real-time audio output. This architecture made MOD the lingua franca of computer music throughout the late 1980s and early 1990s, powering game soundtracks, BBS intro music, and thousands of demoscene productions.

AMR (Adaptive Multi-Rate) is a speech codec developed by the European Telecommunications Standards Institute, designed specifically for GSM and 3G cellular voice transmission. It operates at bitrates from 4.75 to 12.2 kbps, optimizing for the human vocal frequency range (300-3400 Hz). Converting MOD to AMR is a highly specialized use case — the narrow bandwidth codec will strip away most of the musical content that makes tracker compositions interesting. This conversion only makes sense when targeting legacy mobile networks or voice-oriented systems that exclusively accept AMR input.

Certain legacy telecommunications systems, IVR (Interactive Voice Response) platforms, and older voicemail systems exclusively accept AMR-encoded audio. If a developer needs to use a MOD-based melody or jingle as a hold music clip or IVR prompt on such a system, converting to AMR is the only option. The extreme compression (often below 10 kbps) also makes AMR suitable for transmitting simple melodic content over extremely bandwidth-constrained connections.

Some feature phones from the early 2000s could only play AMR files as ringtones, and a niche community of enthusiasts still seeks to convert tracker music into ringtones for vintage Nokia, Motorola, and Sony Ericsson handsets. While this is a nostalgic pursuit rather than a practical necessity, it connects two eras of mobile audio — the Amiga tracker scene that influenced early ringtone composers, and the GSM handsets that brought electronic melodies to billions of people.

The conversion first renders the MOD file through FFmpeg's module decoder (libopenmpt/libmodplug), processing the pattern data, sample bank, and effect commands into a continuous PCM audio stream. This stereo output is then downmixed to mono (AMR is mono-only), low-pass filtered to remove content above 3400 Hz (AMR's Nyquist limit at its 8 kHz sampling rate), and resampled to 8000 Hz. The mono 8 kHz PCM feeds into the AMR-NB encoder (libopencore-amrnb), which applies algebraic code-excited linear prediction (ACELP) to model the signal as a series of pitch pulses and codebook excitations. The encoder operates at one of 8 selectable bitrates (4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, or 12.2 kbps), outputting AMR frames in an RFC 4867 container.