Free online MID to FLAC converter

What the MID format is

MID, commonly identified by the .mid or .midi extension, stores musical instructions rather than recorded audio. These instructions can include note numbers, timing, velocity, tempo, controller events, program changes, channel assignments, and multiple tracks.

A synthesizer, sampler, notation application, or digital audio workstation interprets those events and generates the sound. Composers exchange MID files to edit arrangements, transfer music between notation software and DAWs, control hardware keyboards and synthesizers, or distribute compact musical performances. MuseScore, Finale, Cubase, Logic Pro, Ableton Live, and many hardware keyboards can create or export MIDI files.

What the FLAC format is

FLAC is a lossless audio format that compresses PCM samples without removing audio data. When decoded, a FLAC file reproduces the same samples as the WAV file from which it was encoded, while normally using less storage space.

FLAC is suitable for music playback, archival, and editing applications that support it. Unlike MID, it contains a rendered audio stream, not editable notes, tempo events, instrument assignments, or separate MIDI tracks. The result represents one performance made with the synthesizer, SoundFont, plugins, effects, and settings used during rendering.

How to convert MID to FLAC

Using 101convert.com

1. Open the MID-to-FLAC converter on 101convert.com.
2. Upload the .mid or .midi file and select FLAC as the output format.
3. Start the conversion and download the resulting FLAC file when processing finishes.
4. Play the file and check its duration, instruments, tempo, and ending; MIDI playback can differ depending on the synthesizer used by the converter.

This method requires no installed software. Do not use it for MIDI files containing confidential material unless the service's handling and retention terms are acceptable.

Using MuseScore

1. Open the MIDI file in MuseScore through File → Open.
2. Inspect the imported notes, tempo, instruments, and playback. MIDI import can produce notation changes or assign different sounds from those used when the file was created.
3. Correct the score or instrument assignments if necessary.
4. Choose File → Export, select FLAC as the output format, choose a destination, and save.
5. Reopen or play the exported FLAC to verify the duration, balance, sample rate, and release tails.

MuseScore is useful when the MIDI requires score inspection or manual correction. Its output is based on the installed MuseScore sound library and the instruments selected for playback, not on an audio recording embedded in the MIDI file.

Using FluidSynth and a SoundFont

FluidSynth provides a repeatable command-line render, but it requires a SoundFont, usually an .sf2 file, and a separate FLAC encoder. With FluidSynth and flac installed, render the MIDI to WAV:

fluidsynth -ni soundfont.sf2 composition.mid -F composition.wav -r 48000

Encode the WAV as FLAC:

flac -8 composition.wav -o composition.flac

The -r 48000 option requests a 48 kHz render. Use a different rate when the intended playback or production workflow requires it. The -8 option increases FLAC compression; it does not improve or reduce audio quality, although encoding takes longer. Keep the WAV until the FLAC has been checked, then delete it if the intermediate file is no longer needed.

Quality and compatibility limits

This is a rendering process, not a direct lossless conversion from MIDI. The same MID file can produce different FLAC files with different synthesizers, SoundFonts, plugins, effects, pitch-bend behavior, tempo interpretation, sample rates, or channel configurations.

MIDI files that depend on external hardware, proprietary plugins, unavailable SoundFont instruments, or unsupported effects may render with substitute sounds, missing parts, or silence. Reverb and instrument release tails can be cut off if the export ends immediately after the final MIDI event, so check the ending before distributing the file.

FLAC normally contains a stereo or multichannel audio stream and cannot retain independently editable MIDI tracks. Keep the original MID file with the FLAC if you may later change notes, instruments, tempo, or arrangement. The FLAC will not preserve the original MIDI performance data or recreate sounds that were unavailable during rendering.