Hi Dmanx,
Like most of the people who responded, I can read and write music. Also, like most of the respondents, I'm not all that good at it; i.e., I can't sight-read difficult passages and play them in real time. That said, however, I find that reading music helps, sometimes in unexpected ways, like being able to de-cypher a bass line or a harmony part, even though you already "know" the song.
Understanding a bit of musical theory is even more important. It's just about mandatory for creating horn parts; it helps in anticipating chord changes in unfamiliar songs; and it allows me to create interesting solos and bass lines -- without an understanding of scales and chord patterns, all of these functions are mostly hit-hit-and-miss. I have NEVER been a speed-demon soloist, but I think I create solos that are more melodic than most 100%-by-ear players do.
Regards,
-BW
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Bruce Wahler
Ashby Solutions™
http://music.ashbysolutions.com978.386.7389 voice/fax
bruce@...