This post is part of our Disco 101 program, an in-depth series that looks at the far-reaching, decades-long impact of disco. Curious about disco and want to learn more? Go here to sign up. Already signed up and enjoying it? Help us get the word out by sharing it on Facebook, Twitter or just sending your friends this link. They’ll thank you. We thank you.A revolution in music arrived in April of 1976. And like all good revolutions should, this one began with bongos. The extended percussion break was just one exciting element of the remix -- or “disco blending,” as the credits put it -- of Double Exposure’s “Ten Per Cent,” the handiwork of DJ Walter Gibbons and engineer Bob Blank and the first-ever commercially available 12-inch disco single. When the sales for this seven-minute masterpiece outstripped those of the regular 45 by two to one, the music business swiftly realized the new format’s potential.It’s no accident it was an independent record company, Salsoul, that first gave record buyers a chance to experience the musical mutations that DJs like Gibbons and Larry Levan were concocting in such clubs as the Paradise Garage and Le Jardin. Unencumbered by the girth of the major record companies, the indies had the agility and street-smarts to fully capitalize on the phenomenon, which began in the early ‘70s in Fire Island’s hotspots and David Mancuso’s Loft and pretty much swallowed America whole during Saturday Night Fever mania at the end of ‘77.By then, most majors had their own disco departments eagerly churning out 12-inches, sometimes by rock acts like the Rolling Stones, Rod Stewart, and pretty much anyone else who wanted to get a song on the radio or in the clubs. But the big gears it took to move units for them meant that disco’s greatest innovations were by smaller operators. They didn’t mind the very limited lifespans for fleeting dancefloor faves and hastily assembled, studio-only acts, which didn’t suit majors more interested in the bigger profits that came with album sales and touring artists.This action was its most feverish in New York, disco’s birthplace and epicenter, where companies like Salsoul, Prelude and West End all fought hard for disco dominance. Labels based in other parts of the country -- like Casablanca in L.A. and TK in Florida – got their pieces of the action, too. By staying on top of the latest advances of DJs and the changing tastes of dancers, these labels were able to maintain a steady stream of 12-inch magnificence. And that lasted well after the majors abandoned the dance-music marketplace at the end of the decade, chased away by the disco backlash. There was also such a glut of product, many marvels only got a fraction of the exposure they deserved, which is why these tracks are so coveted by collectors and compilers today.The long-unheard mixes collected on For Discos Only: Indie Dance Music From Fantasy & Vanguard Records: 1976-1981 demonstrates how much incredible music was out there, and how little disco’s much-publicized death impaired the scenes in New York and the West Coast. The enterprising ways of many key indie labels had everything to do with that. Like Salsoul (which began by licensing a chunk of CBS’ Latin music catalog), Fantasy and Vanguard both started with very different kinds of music on their rosters than disco. Fantasy was founded in San Francisco in 1949 as a home for jazz great Dave Brubeck before hitting big with the Creedence Clearwater Revival. Founded in N.Y.C. the following year, Vanguard released many of the most iconic folk and blues recordings of the ‘50s and ‘60s. Listen closely and you can sometimes discern traces of those histories in the labels’ disco-era output, whether it’s in the irresistibly smooth jazz-funk the Blackbyrds cut for Fantasy or the impeccably performed tracks by the Players Association, which got its start when drummer/arranger Chris Hills and producer Danny Weiss began enlisting some of New York’s best session musicians to record covers of smashes like “Love Hangover” for Vanguard.But there are flashes of the future too, especially once Harvey Fuqua – a former Motown producer behind Fantasy/Honey, an Oakland-based disco imprint for the label – united his protégé Sylvester with young electronics whiz Patrick Cowley. With their synth-heavy, ultra-orgasmic sound, Sylvester’s “You Make Me Feel (Mighty Real)” and “Dance (Disco Heat)” spawned their own subgenre: Hi-NRG. Fantasy/Honey’s slate also included similarly exhilarating singles by Two Tons of Fun, two back-up singers for Sylvester – Izora Armstead and Martha Wash – who’d get a lot more famous when they changed their name to the Weather Girls.Meanwhile back in New York, Vanguard became a haven for some of the city’s most skilled disco purveyors. Rainbow Brown was the brainchild of Patrick Adams, a producer and arranger responsible for killer cuts for Salsoul and Prelude. A studio project modeled after Chic and Adams’ Musique by former Weather Report drummer Alphonse Mouzon, Poussez! was more sophisticated than its salacious-sounding name would suggest (but then it would have to be).It’s a testament to the era’s abundance of creativity that so much of this music has been little heard -- especially in their “disco-blended” incarnations -- since they first appeared. To mark the release of For Discos Only, here’s a playlist that relights the fuse for that original indie disco explosion.