If you like Tool, check out my other article about the connection between the lyrics and syllable-structure of the song 'Lateralus' and the Fibonacci mathematical sequence. Some pretty amazing stuff these guys come up with, I tell you

Sir Smittius

I can't say scientifically, although I know for a fact that I can't carry a tune in a bucket when it comes to singing, yet I can play the drums and guitar fairly well and definitely know how to appreciate and "feel" music. So my educated hypothesis would be an unequivocal "NO, you are not tone deaf if you cannot sing in tune!!" My comment though, is that if you are asking HOW to feel the music, you aren't actually doing it. The only way to do so is to embrace ALL forms of music (even those you dislike, and ESPECIALLY classical
Sir Smittius