Convert Standard MIDI (.mid) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or registration.
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MID (Standard MIDI File) is a music notation format storing performance instructions — notes, velocities, timing, instrument assignments — in a compact binary format created by the MIDI Manufacturers Association in 1983. MIDI files contain no audio; they are interpreted by synthesizers to produce sound. File sizes are tiny (10-100 KB) because only performance data is encoded.
AMR (Adaptive Multi-Rate) is a speech-optimized audio codec designed by ETSI for GSM mobile telephony. Converting MID to AMR renders the MIDI through a software synthesizer and then encodes the resulting audio using AMR's narrowband speech compression. This produces ultra-small audio files suitable for mobile voice channels, though musical content suffers significantly from AMR's limited frequency range.
AMR is required by specific mobile telephony infrastructure — MMS gateways, voicemail systems, and legacy feature phones that only support AMR playback. If you need to deliver MIDI-based audio through these channels, AMR is the only accepted format in many telecom systems.
The primary use case is not music fidelity but compatibility. MIDI ringtones or notification sounds destined for older mobile networks must be converted to AMR to function. The resulting audio is heavily compressed and bandwidth-limited, but it plays reliably on virtually any GSM-capable phone manufactured in the last two decades.
FFmpeg decodes the MIDI event stream using its built-in decoder with a software synthesizer and SoundFont. The synthesizer renders all MIDI channels to a PCM audio mix. This PCM is then downsampled to 8 kHz mono (AMR-NB requirement) and encoded using the libopencore-amrnb encoder. AMR-NB operates at bitrates from 4.75 to 12.2 kbps using algebraic CELP (Code-Excited Linear Prediction) optimized for speech. The output bandwidth is 300-3400 Hz — most musical content above 3.4 kHz is discarded.
AMR was designed for speech, not music. The 300-3400 Hz bandwidth eliminates most musical harmonics, overtones, and high-frequency detail. Synthesized MIDI rendered through AMR sounds muffled and distorted — drums lose attack, cymbals disappear, and sustained notes exhibit warbling artifacts from the CELP codec. The SoundFont quality matters less here because AMR's compression dominates the result. Simple melodic content (single-voice melodies, basic ringtone patterns) survives better than complex arrangements.
| Device | MID | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
MID to AMR is a niche conversion for mobile telephony compatibility. The audio quality is poor for music but functional for simple melodic notifications and ringtones on legacy mobile infrastructure.
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| No |
| Funktion | MID | AMR |
|---|---|---|
| Fullstandigt namn | Standard MIDI File | Adaptive Multi-Rate Audio |
| Filandelse | .mid | .amr |
| Bast for | Musical performance data | Speech optimized |