A great way to pad out a piece of music is to compose 2 bars and then transpose those bars to 3 different keys. Then you have 8 bars of music. Do this twice, then make a variation on your previous work, and you have 32 bars.
Transposition MP3, 1:18, 938.12KB
Transposition MIDI, 4.45KB
Transposition PDF, 22.95KB
Transposition Score (Sibelius 6), 40.03KB