Is it possible to play a MIDI file that has my game music in unity?
Since midi isn't imported as an audio file, how can I do this? (plugins maybe?)
I would like to do this in order to play my midi sound files without having to convert them to another format and since they a are weightless.
MIDI is unfortunately not supported, no.
Here is what you should do: Suggest it as a feature on our uservoice site.
Other people that need it can then vote it up and then we'll implement it. It seems to be supported by FMOD, so it could be implemented in a later version of Unity.
We prepare MIDI Unified package. It will be soon in asset store. Supported platforms WIN/OSX.