“MIDI” (Musical Instrument Digital Interface) is “data”. MIDI data can be sent to a synthesizer to create sound. It is the synthesizer that creates sound - the MIDI data just tells the synth what to play, and it will sound different when played on different synthesizers.
To “convert” audio into MIDI, an app would need to analyze the sound and try to detect discrete note pitches. The pitches are then converted to MIDI note messages. Audacity is not that kind of app, Audacity is an audio editor. Apps to convert audio to MIDI do exist, but mostly they are only effective when the audio has a single melody line (one note at a time). Some apps will attempt to convert polyphonic music into MIDI, but they tend to not be very accurate and frequently miss notes, pitch notes incorrectly, or add notes where notes did not exist in the audio. Converting polyphonic audio to MIDI is very difficult and requires specialist software. I suspect that audio to MIDI conversion will improve in the future due to the advances in the field of AI, but currently it is far from perfect, even with the best (expensive) software, an Audacity does not do this at all.
Thanks for the response Steve. This is a piano piece I was hoping to convert so I thought maybe it might be simple enough that it could be converted. I figured something more polyphonic would be likely near impossible…I guess I was hoping against hope!
Did you press your sustain pedal any time in the performance? If you did, that’s the end of the world. The conversion software is going to try to analyze the original note plus the original note’s sustain tones plus the new note and the new note’s overtones and harmonics. Someone trying this conversion might be able to manually sort the notes and reach over and make corrections by hand. I don’t think automation is going to do it.
There’s a social problem with anybody trying to develop automated software. In spite of instructions, everybody with a pulse, respiration, and heartbeat is going to try to convert a multi-instrument or complex song, and they’re all going to be ticked off at you personally when it doesn’t work.
Alternately, that could be the end of your developer career.
Missed one. MP3 gets its small, convenient files by re-arranging musical tones and leaving some of them out. So if you had a fighting chance with a perfect format such as WAV, you don’t have it any more.
Never use MP3 in the middle of production. Nothing good can come of that.