Head-sets are nice, but forget about dynamics, If you can't get away from the mic, dynamics are all but lost. Harmonizers are an interesting tool, they're also as easy to identify as lip-syncing.Other than the Throat Singers from Tibet (or where-ever) not too many people can sing in more than one pitch at one time, so why bother. If your voice is capable of pleasing an audience, then leave it alone (literally). You can become innundated with midi controlled toys, and you can end up being buried in the mix.
In my solo gigs, I use a drum machine for rhythm and accompanyment. Try the simple route, before things get to complicated.
just my thots..
http://members.shaw.ca/shboom

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...L