Free online OPUS to SF2 converter

What the OPUS format is

OPUS is a lossy audio codec stored commonly in .opus files and Ogg containers. It is designed for speech and music at low bitrates, so it appears in voice recordings, Discord and other messaging applications, web audio, browsers, and some recording software. OPUS files contain rendered audio, not MIDI notes, instrument zones, loop metadata, or playable presets.

What the SF2 format is

SF2, or SoundFont 2, is a sampled-instrument bank format. It stores PCM WAV-derived samples together with key ranges, velocity ranges, tuning, envelopes, looping information, instruments, and presets that MIDI-compatible software can play.

SF2 is suitable for FluidSynth, many software samplers, MIDI modules, and notation applications. It is useful when a recorded sound must respond to MIDI pitch and velocity, but it does not preserve the original OPUS compression or automatically turn a complete recording into a multisampled instrument.

How to actually convert OPUS to SF2

Using FFmpeg and Polyphone

1. Decode the file to an uncompressed WAV with FFmpeg:
   ffmpeg -i input.opus -c:a pcm_s16le output.wav
2. Open output.wav in Polyphone, a SoundFont editor, using File → Import or the sample import control.
3. Create an instrument and assign the imported sample to it. Set the sample's root key to the note at which the recording should play naturally; use the sample's original pitch if it represents a single musical note.
4. Set the key range and, if required, velocity range. For a one-shot sound, disable looping; for a sustained note, define loop start and end points and audition the loop for clicks.
5. Create a preset, attach the instrument, assign a bank and preset number, then export with File → Save as to output.sf2.

For a recording containing several notes, split it into separate WAV files first and import each sample into its own key or velocity zone. A sample editor such as Audacity can be used for trimming, silence removal, normalization, and splitting before the SoundFont is assembled.

Using the online converter

You can convert the file on 101convert.com for free without installing software. Download the resulting SF2 and test it in the target sampler, because automatic services may choose a default root key, omit loops, or package the recording as a single playable zone.

Quality, compatibility, and limitations

OPUS is lossy, so an SF2 created from it cannot recover detail removed during encoding. Converting to WAV before authoring the bank prevents another lossy encode, but it does not improve the source quality.

A long song or voice recording is technically storable as an SF2 sample but is usually unsuitable as an instrument: the bank becomes large and MIDI playback merely changes the speed and pitch of the entire recording. SF2 works best with short, clean samples or multisamples recorded at several pitches and dynamics.

Use 16-bit PCM WAV for broad SoundFont compatibility. Mono samples generally consume less memory; stereo is useful for sounds whose spatial character matters but may be unsupported or inefficient in some playback engines. Test the exported bank in the exact sampler or device that will use it, since SF2 implementations differ in support for loops, envelopes, stereo samples, and modulation.