Well i enjoy schooling anyway but sometimes i do wear an ipod and have a play with getting my horses rhythm to match the beat of the music! Try that!
I do get some funny looks tho when im singing out loud without realising it
I normally try to really collect Horlicks' trot, so shes almost on the spot then really push her on to lengthen. You could do this with trot poles, to help. Make them closer to shorten the stride and make them wider apart to lengthen the stride.
Also I "play" about using transitions, as she gets very smart after a few walks to canter and halts to trot!
How about looking into how do you more techincal movements and have a go!! You never know, your horse may learn how to passage or piroette!!