There are performances that yield their secrets demurely, without pretense and with a semi-reluctant grace. This concert disc by the nonet Suspensão is such an offering, the music conjuring a universe of soft hues and back-lit timbres at once murky and gently luminous.

These vast musical forms can only be verbalized as stolen moments, minuscule cross-sections of development frozen by the incompleteness of description. Creative Sources frontman Ernesto Rodrigues leads the group whose instrumentation defies the felicities of categorization. Even when moments of clarity occur, as at 2:00 into the longer of the two pieces on offer, and it's clear the Carlos Santos' electronics are becoming prominent in the texture, the syntax is a fascinating mixture of tonal and atonal elements. Like Alban Berg's violin concerto when the Bach chorale is completely manifest, this improvisation occupies a third space out of which tendrils of brightness emerge. The ear is suspended in the heart-stopping beauty João Gato's soprano saxophone floats over the texture at 11:45, or the delicate shine of José Oliveira's suspended cymbal two minutes later. Luisa Gonçalves' piano cuts through the near-silence opening the second and much briefer piece, itself a more pointillistic affair. Is that electric guitar or electronics at 3:43 of the same relatively brief work? It can be difficult to sort out the textures.

What is certain is that the performance's beauty lies in its subtlety. Even when slightly more jagged, as on that second piece, the nonet favors soft-edged sounds, as if Debussy entered the world of free improvisation. So much collective improvisation arcs toward and then away from a climax, or even a series of climaxes, entering and exiting areas of exploration. True to its name, Suspensão is having none of that. Its music inhabits a twilight realm easily conducive to late-night listening, where thoughts tend to blend along unexpected paths of discovery, and moments of clarity are glimpsed and then disappear. Frottage provides the perfect soundtrack for that existential state.