@JimmyFromTheBay
I've installed the MESS fork for it (lr-mess-mz1500-cass).
What is the MESS fork ?
Please give a better explanation on how you installed.
With this command you can find the supported extensions :
pi@raspberrypi:~ $ /opt/retropie/emulators/mame/mame -listmedia mz1500
SYSTEM MEDIA NAME (brief) IMAGE FILE EXTENSIONS SUPPORTED
---------------- --------------------------- -------------------------------
mz1500 cassette (cass) .wav .m12 .mzf .mzt
These are the loading instructions for MZ-1500 :
Hit C key
TAB > Tape control > Play
I used cassette files inside mz800_cass.zip from mame-sl.
mucmac.zip worked for me.