There's the mechanical ability to sightread and play back on an instrument, and then there's the mental ability to sightread and imagine the sounds.

I can play simple monophonic lines. I'm not a particularly good player, and find that after I've been fooling with the flute, the fingering for the clarinet have gotten muddled. I'm just a hobbyist, with no pretension of ever becoming good... just "good enough".

I can play "chordal" piano, but two-handed polyphonic music is a real challenge - and I've been working at it for years. It just doesn't seem like my brain is wired for that level of coordination.

Theory helps a lot. For example, I can read well enough to see the intent of the composer, and substitute something functionally similar that matches my (lower) skill level.

On a good day, I've can sightread a vocal part with 60% accuracy... but I'm guessing at many of the leaps, when I really should know the pitch. So I've got a long way to go there.

-- David Cuny
My virtual singer development blog

Vocal control, you say. Never heard of it. Is that some kind of ProTools thing?