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How to convert MIDI files to MP3

An RP visitor asks how to convert MIDI files to MP3. Hmmm, this isn't going to be as straightforward as it seems...


Question from a Audio Masterclass visitor...

Can you tell me how to convert MIDI files to MP3 or what equipment I would have to purchase to make this work? This is so I only have to carry a laptop or MP3 player to a musical job, thank you.

John Ciurlino

Here's another question: What's the difference between a MIDI file and an audio file?

Anyone who understands MIDI will think this is a baby question. But I can say from experience that there are plenty of people around who are confused about the difference between MIDI and audio. As we all probably were once.

An audio file contains a digital representation of the sounds actually made during a recording. When replayed, it will sound just like the original. If the original recording was of an acoustic piano, then when the audio file is played, it will sound like the same piano, in the same room, with the same player.

However the recording might have been made on a digital piano, and rather than taking the audio output, the MIDI output was used.

MIDI (Musical Instrument Digital Interface) carries information on which keys were played and how hard they were played. This can be recorded as a MIDI sequence and then stored as a MIDI file.

The MIDI file cannot be played back directly as it contains no audio. It only contains information about which keys were pressed, and how hard they were pressed.

So it must be directed to a sound generator of some kind. This can be software on a computer - Windows Media Player and QuickTime will both convert MIDI to audio. Or it can be a standalone sound module.

Windows Media Player and QuickTime can both play audio directly from a MIDI file as they have built-in sound generators. To replay through a standalone sound generator, the MIDI file needs to be converted back to a sequence.

When the MIDI sequence containing our original digital piano recording is played through a sound generator set to an acoustic piano program, then the original notes of the performance will be replayed by the sound generator.

It will sound like a piano, but not the same piano as the original. The acoustic will be nonexistent, unless artificial reverb is applied. The relative loudness of the notes will be altered because the response of the sound generator to that data will be different to the original digital piano.

So it will sound a bit like the original performance, but nowhere near exactly the same.

So in a nutshell, to convert a MIDI file to MP3, firstly it must be replayed through a sound generator (or equivalent software), the output of that sound generator recorded as a .WAV or .AIFF file, then that file is converted to MP3.

Software can make this process easier, but to get the best results you would have to be very choosy about which sounds are used for playback, particularly with a complex arrangement.

In conclusion, it's all very do-able, just a bit longwinded. Rather you than me!

Here's a link that might help...

By David Mellor Monday June 5, 2006
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