I'd guess they use .mod files - instruments and tracks, rather than digitized audio.
1.44Mb should be enough even for a compressed but still decent quality MP3(~128kb) or AAC(~112kb) short track (1:30+, I think), then you can also reduce audio quality and gain more time based on music styles (lo-fi, etc).
MP3(~128kb) or AAC(~112kb) are alrwady reduced audio quality.