James Cotton

Answer 1

His harmonica of choice is the Hohner Marine Band, in several keys. So he uses a different key for each song.
This harmonica has a very sharp, cutting sound. It has been manufactured for over 100 years!

Answer 2

James in his early years used an old "Astatic" brand mic, through a tube amp. It gave a dirty sound, which at the time was meant to imitate a saxaphone.
Later years until now it became impractical to have this older sound (although loved still by many players), particularly with the advent of the bigger sound systems and larger venues. So he will play through a Shure SM58, the standard vocal mic for years of most performers.
This gave a distinctive cleaner sound but no less big!