So here's my thoughts on the various musical talents of some of our friends:
Claude has a beat up old acoustic guitar that he sometimes takes out with him around town. He enjoys sitting down on someone's stoop and playing soft music to fuck with passersby. If people walking down the street stop and try to figure out where the music's coming from, Claude considers his day a success.
Nathan used to play the French Horn when he was younger. He felt it sounded like it was more important than all the other instruments, and he could relate to that. However, by the time he'd gotten to high school, Nathan had given up his pursuit of a musical talent because he thought that playing music was a waste of his time.
Peter, on the other hand, played the viola and was quite talented. While he couldn't play well at first, he kept practicing and one day things just clicked for him. Once that happened, Peter just kept getting better and better, always sitting as first chair in his school orchestras. Although he hasn't practiced in years, Pete could pick up a viola right now and play nearly perfectly.
Matt took piano lessons as a kid, but was not good, at all. Mostly because he'd rarely ever practice. He took lessons for nearly three years, however, and still remembers which keys are which. But he's forgotten how to read music, which he never really understood to begin with. The only thing he was ever good at was keeping time. Interestingly, this same skill would make him fairly skilled as a percussionist. But he's never even thought about picking this up, as he just assumes he has no musical talent.
Sylar was a virtuoso at the piano from the time he was six. His performance would make you weep openly, he's so good. Virginia would often force him to play pieces for church events, something he detested. Because of this and because it was never really challenging for him, Sylar hasn't played much since his early teenage years.
Tracy played the flute in grade school. She liked how playing an instrument got her out of class twice a week, but was less enthusiastic about the flute at all other times. To her, the flute was more of an accessory than anything else. Once she got to junior high, Tracy decided to stop playing the flute altogether.
Claire has absolutely no musical talent, whatsoever. None.
Growing up in India, Mohinder was always fascinated by the snake charmers that could always be found in the parts of the city most frequented by tourists, performing for donations. He secretly wanted to learn to play one of the flute-like gourds the snake charmers used, but knew that Chandra would never in a million years allow this. Later in his life, when he was studying in Cambridge, Mohinder joined the University Chamber Choir on a whim and discovered that he was quite a talented singer (a baritone, if you were wondering). He subsequently joined the Cambridge Madrgials and even toured with them, briefly, one Christmas.
Noah grew up, musically speaking, in the mid-to-late '70s with The Who, Pink Floyd, Led Zeppelin, and Aerosmith among his personal favorites. As a result, Noah plays the electric guitar surprisingly well. He played in two bands during his college years, but gave up that part of his life upon meeting Sandra. It's not that Sandra made him stop, mind you; he simply enjoyed spending all his time with her more than he enjoyed playing with a band. Although his skills have waned a bit, over the last 15-20 years, he would still surprise you with some of the things he can make the guitar do.
Ando has never played an instrument, but would kick your ass at Guitar Hero.
Hiro was made to play the violin as a child, but was too undisciplined to practice and never became any good at it. This was a grave disappointment to Kaito, who considered the ability to play an instrument as a testament to one's character. Hiro's mother was more sympathetic to her son, as she had gone through something similar (although with the clarinet) in her youth.
And lastly, West thinks he's a great DJ because he owns turntables. But he's actually pretty bad. His mixes are hackneyed, at best.