SMG does a nasty trick of setting the frequency to 1 and leaving the
attenuation unchanged, instead of setting the attenuation to 15.

It does this
a) when sound effects are not playing
b) in the short pause between music tracks playing

A frequency of 1 is so high pitch and so people don't notice much.
However, in MEMU, especially on Windows, it can be clearly heard.

The patched SMG2M.COM changes a) to set the attenuation to 15.
Therefore most of the problem is removed.
Patched byte is around 0x23f3 in memory.

I've not worked out an easy patch for b) as yet.
