Flotation Device pays homage to Michael Tilson Thomas as a pianist, composer and—above all else—a conductorial advocate for new music, as exemplified in two of our favorite recordings of his that showcase American experimentalism at its craggy and confrontational best. We also mark the 50th anniversary of Xenakis’ Psappha with three very different interpretations of that most iconic of all solo percussion works. Plus we survey new albums by Melvin Gibbs, Brandon Seabrook and Marilyn Crispell, along with an Ornette Coleman Third Stream curiosity that’s just been revived after decades on the shelf. Sofia Gubaidulina’s uniquely somber Concerto for Bassoon and Low Strings gets its own 50th birthday nod, and a preview of a Meany Center recital by Melia Watras (with several world premieres on the program) rounds out the offerings.