It is quite interesting. I've been playing music since I was 3. For me, music is almost a second language, and I often feel like I am speaking when playing music. Occasionally I'll stutter on a note and I feel the same blocking feel in my head that I do when I can't say a word. The nice thing about music is I can sort of roll with it and make it part of the musical phrase and style. My theory is I'm using the speech centers of my brain sometimes when playing music and that's where the stutter originates. I think it would be fascinating to do a brain scan to see what areas are active when stuttering speech, speaking fluently, stuttering music, and playing music fluently.