Also known as G.A.S.
This condition afflicts musicians and singers of all kinds, but seems to be especially virulent in electric guitar players. It is typified by an uncontrollable urge to buy, beg, borrow or steal the latest piece of musical equipment seen in a store, in a magazine, on TV or on another musician.
Poverty is the only known prevention (and only known cure) for the disease.
G.A.S. is the most likely explanation for any musician who possesses more than the required number of his/her chosen instrument (ie more than 1), but is more usually seen in the miriad unnecessary musical accessories hidden around the victim's room - such as amplifiers, electronic tuners, fold-back speakers, amp stands, gigantic speaker and PA stacks, guitar polish, guitar polishing cloths, several grades of strings, multiple gig bags full of things which buzz, click or glow in the dark, and, and, and....