What about -mmin?
find /var/www/html/audio -daystart -maxdepth 1 -mmin +59 -type f -name "*.mp3" \
-exec rm -f {} \;
From man find:
-mmin n
File's data was last modified n minutes ago.
Also, make sure to test this first!
... -exec echo rm -f '{}' \;
^^^^ Add the 'echo' so you just see the commands that are going to get
run instead of actual trying them first.