Buddy Holly stutters. John Lennon stutters. Are their stutters copyrightable expression?

Is a stutter unmusical? Could something as unmusical as a stutter be subject to copyright protection? If a stutter is sung, is it more likely to be musical? If a stutter is musical, is it more likely copyrightable? Could "stutter" be simply a stutter, or a well-crafted, complex vocal articulation that is musical, difficult to reproduce and original expression that is subject to copyright protection?