Quick check on /opt/maesynth/*py files revealed that they are loading wav files from /home/opt/maesynth/......... while it is actually installed to /opt/maesynth....

Although standard N900 systems have a /home/opt, it wasn't the case for mine. I moved /home/opt to some other location to make /home look cleaner, hence it couldn't find required png & wav files.

A simple command fixed the issue though:
sudo gainroot
cd /opt/maesynth
sed -i 's!"/home!"!g' *py

... and with above (& after ensuring system isn't muted), maesynth lived happily ever after.
Hope an update gets trickled into the source for this one.

Best regards,

kh