A cellist plays in duo with electric guitar, their music wrapped in an envelope of reverb and static from the computer processors onstage. </p><p>A saxophone and bass clarinet perform acoustic compositions by acclaimed 20th-century composers in tandem with new electronic pieces by younger ones, interspersed with a live contribution from a DJ. </p><p>A composer who wants to form a new-music group turns not to conservatories but to Craigslist. </p><p> Classical music is thought of as a world of formal wear, red velvet seats and Mozart concertos. But young classical musicians around the country are increasingly exploring additional ways to express themselves. Once upon a time, young conservatory musicians wanted to grow up to play as soloists with major orchestras. Today, many of them are forming bands instead. </p><p> The ensembles of the new alt-classical world are poised somewhere between traditional classical music and contemporary culture. It&rsquo;s hard to define exactly what kind of music they play. </p><p> &ldquo;It always seems to be so many adjectives,&rdquo; says Gina Biver, a composer and founder of the Fuse Ensemble. &ldquo;You just say contemporary art music or modern art music; that&rsquo;s close. We have scores written out. All our musicians are classically trained. We have cellos and contrabass, but I also play electric guitar.&rdquo; </p><p> What&rsquo;s certain is that, following in the footsteps of groups like the Kronos Quartet and the Bang on a Can All-Stars, these ensembles perform any and all music, from Steve Reich to Radiohead, Javanese gamelan to the Renaissance composer Josquin, in instrumentations that might include anything from violin to (in the case of the Great Noise Ensemble) amplified Coke cans. </p><p> And unlike traditional classical groups, you can&rsquo;t even tell what they are by their names. Instead of the Juilliard Quartet or the St. Paul Chamber Orchestra, we have Alarm Will Sound, Eighth Blackbird, Itsnotyouitsme. </p><p> This isn&rsquo;t some lunatic fringe of experimentalism.</p><p> The spirit of these groups is permeating, and invigorating, the whole classical music world. Armando Bayolo, who founded the Great Noise Ensemble through the abovementioned Craigslist announcement, knows his model: &ldquo;I really feel groups like Alarm Will Sound and Eighth Blackbird represent the future of classical music.&rdquo; </p><p> There are two main aspects of the alt-classical idea. On the one hand, it represents an attempt to break down the traditional concert format, which can seem stiff and off-putting to the younger crowd that all musicians these days would like to attract.</p><p> But the second main point about alt-classical groups is that they are increasingly featured on mainstream, traditional concert series and orchestra programs.</p><p> The Library of Congress series, committed to new music since its inception, has presented Alarm Will Sound and the Absolute Ensemble, both &ldquo;bigger groups that are at home in so many worlds,&rdquo; says Ann McLean, one of the library&rsquo;s three senior producers for concerts and special projects. </p><p>Young musicians today, she says, &ldquo;go back and forth with more ease than you would have heard five years ago.&rdquo; </p><p> As different as they are, these new groups do see themselves as part of a sea change in the field. </p><p> Said Nick Kendall, a 31-year-old violinist with the bluegrass-jazz-uncategorizable, classically trained string trio Time for Three: &ldquo;I think there is 100 percent similarity, in that we all come from the same breed, we all trained in the same way. But we all are experimenting and coming up with our own individual voice. I think it is so exciting.&rdquo;