Hi Jill
Welcome to Synthzone and congratulations on your new keyboard (PSR2100).
I almost exclusively play (both my Tyros & PSR2000) in 'full' fingered mode, and fully agree (with you) that this provides a much more natural realistic performance, especially (of course) with the 'left' voice turned 'ON'.
The #1 ingredient to a more convincing LIVE (vs canned) pro arranger kb performance is to make sure that you're playing LIVE as much as possible 'throughout' the song, keeping the auto accompaniment to function only as a background/supporting role.
With styles which include piano/keyboard auto accompaniment parts, I ALWAYS mute (or delete) them and make sure that I play these parts LIVE myself (left voice). I particularly find most 'auto accompaniment' piano/keyboard parts to sound pretty stiff (canned), and that playing them LIVE with more creatively played & varied full chord voicings (both root & rootless) adds a dramatic degree of realism to provide a much more LIVE (realistic) sound. I urge everyone to develop full left hand chord playing keyboard skills if at all possible. This way, in addition to playing the right parts live, adding fully voiced left hand chord played live, decreases the amount of auto accomp (canned) parts (instruments) heard. I typically restrict asssignment of the left voice to: piano, organ, synth, or strings.
Scott
