Free online SMF to FLAC converter

SMF files store MIDI performance instructions, but many audio players and mastering workflows require an audio file such as FLAC. Converting one therefore requires rendering the MIDI through an instrument or synthesizer before encoding the resulting audio losslessly.

What the SMF format is

SMF means Standard MIDI File and is commonly stored with the .mid or .midi extension. It contains note numbers, timing, velocity, instrument changes, controller data, tempo, and other MIDI events rather than recorded sound.

Notation and composition programs such as MuseScore, Logic Pro, Cubase, Ableton Live, and many hardware sequencers can create SMF files. You encounter them when exchanging arrangements, importing a song into a digital audio workstation, distributing backing tracks, or moving compositions between MIDI-compatible devices.

What the FLAC format is

FLAC is a lossless audio format. It stores decoded audio without discarding samples, usually using less space than WAV or AIFF, and supports metadata such as artist, album, title, and track information.

FLAC is suitable for archiving a rendered composition, editing in audio software, sending a high-quality master, or playing the result in applications that support lossless audio. It does not preserve editable MIDI events, separate MIDI channels, notation, or the choice of virtual instrument.

How to actually convert SMF to FLAC

Using FluidSynth and FFmpeg

This method gives direct control over the synthesizer and SoundFont.

1. Install FluidSynth, FFmpeg, and a General MIDI SoundFont such as FluidR3_GM.sf2. The SoundFont supplies the instrument sounds missing from the SMF.
2. Render the MIDI to a temporary WAV file at a suitable sample rate:
   fluidsynth -ni FluidR3_GM.sf2 composition.mid -F composition.wav -r 44100
3. Encode the rendered WAV as FLAC:
   ffmpeg -i composition.wav -c:a flac composition.flac
4. Play composition.flac and check the start, ending, tempo changes, sustain pedals, program changes, and percussion before deleting composition.wav.

Use -r 48000 instead of -r 44100 when the project requires a 48 kHz delivery rate. FFmpeg's FLAC encoder is lossless; changing the compression level affects encoding time and file size, not audio quality.

Using MuseScore

1. Open the SMF in MuseScore with File → Open.
2. Confirm the instruments, tempo, key signature, time signature, and playback result. MIDI program mappings may not match the intended instruments.
3. Export an uncompressed audio file through File → Export, choosing WAV if available.
4. Convert the WAV with ffmpeg -i exported.wav -c:a flac composition.flac.

MuseScore is useful when the SMF also needs notation correction, but its playback result depends on the selected sound library and MuseScore version.

Using the online converter

You can use the built-in converter on 101convert.com for free without installing software. If it offers instrument or SoundFont settings, select them before conversion; otherwise, the service's default MIDI synthesizer determines the audible result.

Quality, compatibility, and limitations

An SMF has no fixed audio waveform, so two conversions can sound different even when they use the same MIDI file. The synthesizer, SoundFont, channel routing, effects, pitch-bend range, tempo interpretation, and controller handling all affect the FLAC output.

Verify that the chosen renderer supports the SMF's format-0 or format-1 tracks, system-exclusive events, tempo maps, lyrics, and sustain or expression controllers. Some SMF files depend on proprietary hardware sounds or custom drum mappings that General MIDI software cannot reproduce.

FLAC preserves the rendered samples exactly, but it cannot restore MIDI editability. Keep the original SMF and the SoundFont or instrument library alongside the FLAC if the composition must be reproducible later.