Singer-songwriter Gavin DeGraw looms -- large or small, time will tell -- on the pop horizon. Building on the buzz from his local club gigs, he recently signed with Clive Davis's J Records and is now recording his debut. A son of musicians, DeGraw, 25, grew up in the Catskills ("I was a cradle singer -- started singing before I could talk") and had his epiphany at 15, at a Billy Joel concert ("Afterwards, we got in the car, and I said to my parents, 'Well, I think I know what I wanna do now' "). DeGraw moved to New York in 1998 and has performed regularly, accompanying himself on piano and guitar. Wholesome and polite, he writes and sings straightforward, easy-on-the-ears tunes in an appealing, precociously soulful voice. "You start kissing her and whatnot," he said at a recent, packed showcase at Joe's Pub, introducing yet another relationship song, "and she starts saying her ex-boyfriend's name. Personally, it never happened to me, but if it had, I'd be very upset. And it would make me write a song about it."