I'm familiar although not comfortable playing in all keys. By that I mean you just don't see many songs done in F# .
I do use the transposer to move songs to fit my voice. For EX. I may want to sing in B but use the transposer to play in C which is much more comfortable.
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Bill in SC --- Roland BK9 (2) Roland BK7M, Roland PK5 Pedals, Roland FP90, Roland CM30 (2), JBL Eon Ones (2) JBL 610 Monitor, Behringer Sub, EV mics, Apple iPad (2) Behringer DJ mixer