In the late renaissance, there was a much debated but fascinating trend in A Cappella choral music known as Musica Reservata, or Musica Secreta. Though the original meaning evokes compositional style more than any kind of veiled practice, my prankish side insists that, with this disc of solo cello and bass improvisations, Marcio Mattos gives us a glimpse into his own secret music. David Ilic's notes spell out the cello's place in Mattos' musical biography, the instrument's gradual return to his performing as a completion of the bass.

Mattos is as creative as ever in these mainly undated concert recordings. Like Paul Rutherford or Derek Bailey, there seems to be very little in the way of impedance between Mattos and his instrument, as demonstrated by the stunning "The Diamond Ring," a three-and-a-half minute precis of the cello's timbral and registral possibilities as imagined by this veteran improviser. For an alternately heated and ice-cool dose of the electronics he uses so tastefully, listen to "Bailey's Beads," another cello extemporization with an absolutely gorgeous slide into layered harmonics at its conclusion. That semistatic world is explored again in the opening moments of "Solwind" , before the jump-cut freneticism vies with microtonal electronic passages in rapid succession.

As with Bob Dylan's Blond on Blond, the miniatures lead to the vast concluding piece, the epic "Prominence," lasting over twenty minutes. My guess is that the 2010 recording uses only bass and electronics, though there is so much happening from moment to moment that such concerns become secondary in the face of high-level creation. Mattos is a creative genius, and to think of this disc as another solo offering is to sell it short. His invention is unparalleled, as is his musicianship, and the minor-inflected and then chromatic opening of "Filaments of Imagination" shows, if any further proof were needed, that tradition lurks in the wings, informing rather than subjugating every note he plays. Don't miss this one!