That's the thing...when is it "useful"? If you can sight read it perfectly, then clearly it's useful. How about if can sight read it with a couple of flubs? Is that useful? How about if you need to scan it and maybe make some marks before you can play it...maybe you need to take it to the woodshed for 20 minutes.
To me "useful" is any of the first three. Reading perfectly obviously qualifies, sight read witha couple of flubs would be the norm for people that can read I think. So that definitely counts. scaning it before playing shows a general knowledge so that wold count. I don't think that taking it to the woodshed, pulling out your old high school book and looking up the fingerings for each note for 20 minutes counts though..
'd love to get other people's version of what counts as "being able to read"
