Tristeza, Friday, November 3, at the Raven, with Dressy Bessy, Plus Ones and the Oranges, is in love with the finer points of instrumentation. The quintet, which operates unapologetically without a vocalist, straddles both emo and rock styles while transcending the usual constraints of rock-and-roll songwriting. Hardly an art project, though, the band also eschews many of the conventions employed by indie instrumental acts: It doesnt aim to impress its audiences with pendulum swings of mood and tempo, nor does it parade an over-indulged set of chops through its songs. Rather, Tristeza cuts through ethereal soundscapes with a sometimes playful, sometimes introspective blend of bass, keyboards and paired guitar melodies. With a sound reminiscent of a postmodern Tangerine Dream, Tristeza is impressive but not showy. Its music shimmers with a detailed intricacy that somehow appears effortless.