@JosDuchIt
Try to keep it simple, this should work
DELETE T:music FORCE QUIET
REQUESTFILE TITLE="Choose your music" ACCEPTPATTERN="*.(mp3|mod|wma|m4a)" TO T:music
IF NOT WARN
;play music command goes here, eg.
playtunes <T:music
DELETE T:music FORCE QUIET
ELSE
ECHO "No Music"
ENDIF
If the redirection doesn't work try:
IF NOT WARN
SET m `TYPE T:music`
playtunes "$m"
UNSET m
ENDIF
or simpler:
IF NOT WARN
playtunes `TYPE T:music`
ENDIF
If IF NOT WARN doesn't work you can use IF EXISTS T:music instead as the file isn't created if you cancel the requester.
edit: changed code a little to remove pointless if exists check.