I read somewhere that no lyrics is best - don't know what you were planning? The experts say pick something that has a rhythm that suits your horse's best pace. Not sure what you meant by no choreography. Won't you be practicing a routine?
Depends on what type of impression you want to give to people watching.
I did a test to music once on my horse Stanley and he was a bit 'quirky' but in a funny way..... sometimes you only had to watch him in the stable and you'd be in stitches laughing!
I decided to do the test to a song called 'DOOP' by Doop..... if you search youtube for Doop Doop......its brilliant!
Its upbeat and has clear places where you can time your canters and rein changes.... and if you mess up it wont matter because everyone is bopping.... very catchy and amusing!
However..... a friend of mine used to do a test to a song by Enigma called 'Sadness part 1'......... beautiful test music for the right pony!