In the old Viruses, a Multi simply 'pointed' to destinations of patches in the Single banks, therefore if you edited a patch in Single mode, it would also change all the Multis that pointed to that patch.
In the TI things are different and better. The 'Multis' are actually banks of slots available for loading in entirely new 'Singles' for layering together. Instead of the Multi simply pointing to patch destinations in the Single banks, the Multi now hosts its own single patches within the Multi, meaning you can tweak all the patches in the Multi bank independently and it wont affect anything else, and similarly you can tweak all the patches in the Single banks and it wont affect the Multis.
Consider Multis as being new banks of patches for either layering or sequencer use.
PS > Welcome.
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PS > And another thing! Will the Ti|3 have user customisable/importable wavetables?
A ribbon-controller or XY-Pad might be nice, too, please! Thanks!