My 3-minute GB song has turned into a 10GB file

[rsherid]

I have a completed 3-minute song with real vocals/bass/guitar plus the max. amount of synth tracks. I've locked everything, but it still won't play on my MacBook - 4GB RAM/2.2 Ghz Intel Core 2 Duo - due to the error, "Too many instruments in real time."

I'm moving the project over to an external HD to see if it'll play like there, but I can't figure out why it won't play. It worked fine last night. And how did it grow to be 10GB in filesize? Because I locked all the tracks?

 

[robduckyworth]

How many takes did you have of each part? they are all saved in the audio files area, bearing in mind that 1m = 10MB with an uncompressed audio format.