change the b value (beat, tempo) to something higher:
Imperial:d=4,o=5,b=400:e, e, e, 8c, 16p, 16g, e, 8c, 16p, 16g, e, p, b, b, b, 8c6, 16p, 16g, d#, 8c, 16p, 16g, e, 8p
Use this online converter/player to ear and tweak to your liking.
http://midi.mathewvp.com/rttl2Midi.php
and read more about RTTL at Ring Tone Text Transfer Language - Wikipedia
/Camille