To answer your question: Aren't the sounds in ANY synthesizer GM? As far as I know every hardware synth has a GM set.

Most if not all also have a large number of "better" sounds. I put better in quotes because I guess it is in the ear of the listener, isn't it? Anyway, GM is fine for working on things, but usually you want something that sounds much better, in my opinion. Those sounds are all available and accessible on hardware synths, you just have to use the documentation to know how to tell whatever program you are using how to find them. Patch maps are very useful in BIAB and Real Band. There are many already created for most of the major synths, and you can find most anything you need with a quick internet search. These ease the process of selecting something other than a GM sound for a particular part when using BIAB or Real Band.

See, clear as mud.

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