I can't agree. A musician is someone capable of making music to a certain standard, whether by singing, playing a traditional instrument, or electronically. An amateur can be a musician - just not a professional musician - though to my mind they have to reach, as I say, a certain level. I play recorder, for example, but couldn't be called a musician. A promoter, music journalist or producer might be said to be in the music profession but having a career in music, if language is to mean anything, doesn't qualify a person as a musician.