Calling DJ Trackstar (né Gabe Moskoff) the city's best hip-hop DJ is spot-on but woefully inadequate. Spot-on because the 26-year-old slays on the turntables (and distributes astoundingly tight mixtapes at the rate of about one every ten minutes). Woefully inadequate because DJ-ing is just part of what makes Trackstar so vital to the St. Louis scene. For the past several years, he has been a true leader in hip-hop education and activism. The Wash. U. grad takes what he knows (business) and what he loves (music) and combines the two to help the kids coming up. His nonprofit mentoring program, Center for Recording Arts, pairs St. Louis rappers, DJs and producers with high school students; the result is an intense, fruitful crash course in everything from hip-hop history to the finer points of beat-matching. Catch Trackstar at one of his many gigs — he's in residence at the Halo Bar (6161 Delmar Boulevard, St. Louis; 314-726-1414 or www.thepageant.com/halo.html) every Friday night — and know that when he gets that far-off look in his eyes, he's planning the Next Big Thing.