Is there any way to make the file sizes of the songs smaller?
MP3 files are compressed so they will offer you smallest size of the three formats. WAV and AIF files are uncompressed, so they will be larger. (See this Wikipedia article for an explanation.)You can use one of the tools above to reduce the quality of the track to make its size smaller. In particular, if the track is just used for background music, it is sometimes OK to use it at a lower quality.