In 2011/12 I started a kind of songwriting challenge - each month various parameters would be randomly set:

1. Track Length
2. Track Speed
3. Genres
4. Instruments
5. Key of track
6. Number of vocals
7. Lyrics source
8. Other instructions (Oblique Strategies)

I would then ask other musicians to create a new piece of music in response to these parameters. For example, in month 6 (the last challenge) the parameters were set as:

TEMPO – 100-110 bpm
LENGTH – Between 1 & 2 minutes
KEY – C sharp/D flat
NUMBER OF INSTRUMENTS – Two
INSTRUMENTS – Percussion & Woodwind (plus drums, bass, etc)
NUMBER OF VOCALS – Two
LYRICS – From a film
NUMBER OF GENRE INFLUENCES – Three
GENRES – Interview (!) | Surf | Breakcore
OTHER INSTRUCTIONS – 2: “Give the Game Away” & “Look at the order in which you do things”

To see each of the challenges visit the Mosaic Music pages on my blog