Convert MID to AAC — Free Online Converter

MID (Standard MIDI File) stores musical performance data — note events, timing, velocity, channel assignments, and controller messages — in a compact binary format typically under 100 KB. Created by the MIDI Manufacturers Association in 1983, MIDI is the universal language for electronic music communication. It contains no audio; playback depends on an external synthesizer to produce sound.

AAC (Advanced Audio Coding) is the dominant lossy audio codec used by Apple Music, YouTube, Spotify, and virtually every streaming platform. Converting MID to AAC renders the MIDI performance through a software synthesizer to produce an audio waveform, then encodes that waveform as AAC. The result is a universally playable audio file derived entirely from MIDI instructions.

MIDI files are not audio — they are sheet music for computers. Every device and synthesizer renders MIDI differently, producing inconsistent playback experiences. Converting to AAC creates a definitive rendered version that sounds identical everywhere, from iPhones to web browsers to car stereos.

AAC is the standard codec for Apple's ecosystem and the web. Publishing MIDI compositions as AAC enables streaming, embedding in web pages, uploading to music platforms, and sharing through any messaging app. The recipient hears exactly what you intended, regardless of their device's MIDI capabilities.

FFmpeg's MIDI decoder reads the SMF (Standard MIDI File) header to determine format type (0, 1, or 2), tempo map, and time division. A software synthesizer (FluidSynth or similar) loads a SoundFont bank and processes each MIDI event — note-on triggers sample playback with velocity-scaled amplitude, note-off releases with ADSR envelope, program changes switch instrument patches, and control changes adjust volume, pan, expression, and effects. The resulting PCM audio stream is encoded to AAC-LC using the native FFmpeg AAC encoder or libfdk_aac at the specified bitrate, then wrapped in an M4A (MPEG-4 Audio) container.