Finally it's here:
http://macos9lives.com/smforum/index.php?topic=1222.msg4891#msg4891I think I can achieve a very good use of it...
Plugsound Free can be used to open most of the old version of the UVI engine based libraries (.dat format). May be some of the first Mach Five libraries even.
Just rename the (monolith) library file alias you want to open as "Plugsound Free.dat" and enjoy!
If you wish to do the same to several libraries there is a different procedure with a few more steps to do:
1- With Res Edit Rename the resource aEff as you wish.
2- With HexEdit find for "Plugsound Free" and replace with a different string but with the same charecters length.
3- Rename the (monolith) library file alias you want to open with the same string you have used in 2.
and enjoy!
... I'll wish to test this new trick with MSI.dat (Motu Synphonic Instrument)