Wav, Midi and Mp3 – When should I use what?
So when should I use which type of file format? Well, that is largely a matter of personal preference. Before I tell you my preference, here is some information about each format.
Wav files are pure, uncompressed digital audio. It is an actual, digital recording similar to that stored on a CD. Uncompressed digital audio is the only true "CD quality" audio. But wav files can be massive. Even a short track can take up 20 or 30 megabytes of space, often much more.
Midi stands for "Musical Instrument Digital Interface". Midi files do not actually contain music recordings, instead they hold a set of instructions on how to play a tune. Midi files are very small which is good if you plan to have a downloadable version of your game on a website. The quality of playback dependents on the sound card of your user's machine. A Midi sequence that sounds great on a high-end card may sound terrible on a cheap one. Also, Midi is for instrumentals only, not vocals.
As with wav files, mp3 files are actual digital recordings. But the major difference between mp3 and wav is that mp3 files are compressed, and are typically one-tenth the size of uncompressed files. Because mp3 files are compressed, they are a lossy format. This means that depending on how they are compressed, a certain degree of quality will be lost. However, you can still get "almost" CD quality audio from an mp3 file as long as the compression settings are right. Also, mp3 files are a "streaming media" that means that when they are played the whole track is not loaded at the start. Instead, only a part of the track is loaded from disk at a time as it is required.
I would say that you probably want to use mp3 or midi files for background music. Especially if you want your users to download you game from a website. Mp3 and midi files are both small and therefore good for long background tracks. I would then tend to use wav files for short sound effects like explosions and power-ups for that extra bit of quality. If file size is not a problem, then why not use wav files for all sounds and music?