i was thinking ab for Bb,,

but recently on rocksmith the thrill is gone was played in first position on the b note on the e string which tells me their version is in the key of b.

so that would mean i would need an f harp to go with b blues with the key bb is playing right ?

i can't really find an answer online  about what keys does bb play mostly in.

I guess the question is did bb king play in the standard keys of a, e, as much as b, eb, and bb?

also the thrill is gone is in bm ,, is there any good harmonica that play in bm and if so would you just buying it for that one song ?

Third position fits "The Thrill is Gone" and many other B.B. King tunes. It's a very good position for songs in a minor key. Just play a harp that's tuned one whole step below the key of the song, so if the song is in the key of B you would play an A harp. If the song is in C you would play a Bb harp, etc.

thanks jerry potnoy, i guess third position is yet another nunce of the harmonica to try to learn and possibly master some day . :)