Have you tired the Melody driver from aminet?
http://aminet.net/driver/audio/MelodyDriver.lhaI have a prelude, and among the software was a test program to test the audio output....ie it addressed the hardware directly. Is there such a program with your melody distribution?
If it has tocotta emulation (the prelude does too) then maybe you could try using a program that works with tocotta (octamed sound studio does if I remember correctly).
AHI isn't the easiest thing to set up,so maybe there's something wrong in the settings?
