This is best illustrated here by Julian Carrillo's Prelude to Columbus, a work for voice, flute, guitar, harp, and string quartet. Carrillo, one of the true pioneers of this kind of music, uses quarter-tone (and narrower) intervals both as ultra-expressive passing tones and to create fresh, dark harmonies.

Another approach to enlarging the palette of notes is to refuse to accept the compromise of equal half-steps and instead use scales whose notes coincide with "natural" overtones. Harry Partch was the pioneer of this approach and is represented by his Finnegan's Wake songs. Soprano Meredith Bordon is the able soloist in both Partch's and Carrillo's compositions. Her recital-style voice is accurate and strong. Lou Harrison, a follower of both Partch and Charles Ives, contributes a typically attractive Tombeau for Ives, using his own adaptation of Partch's ideas.

But the stand-out performance on the disc is Ives' own Second String Quartet. Harmony Ives once instructed a copyist not to "correct the spelling" of her husband's scores. (For instance, not to turn an E-flat into D-sharp, for these notes, identical pitches in standard notation, are different pitches in a "natural overtone" scale.) She went on to explain how Charles perceived the relationship of such putatively identical notes. AFMM leader Johnny Reinhard realized that she was describing a natural-overtone scale system of 21 notes, and this is billed as the first recording to play this great string quartet in this manner. A valuable alternative to great standard readings, this performance reveals a softer, dreamier, less satiric affect.

The music discussed so far is all tonal. In Anaktoria, Iannis Xenakis writes atonal music, so all the notes are equally valid and nothing sounds out of key; that is to say it is consistently dissonant. Xenakis' sound is bold, generally harsh, without melody or traditional rhythm, but conveys a sense of power and monumentality that is exhilarating (assuming it doesn't send you running for the door instead of listening!). This is an excellent performance, aided by the precise intonation of the experienced AFMM players. Along with the Ives, Anaktoria is a primary reason for my strong recommendation to daring listeners. Giacinto Scelsi's eight-minute piece also is atonal and uses micro-steps--but like most of Scelsi's work it fails to reveal anything of real musical value. Obviously producing a labor of love, Reinhard and his musicians give exciting, committed readings. Sound is slightly studio-bound, but clean. In sum: The disc is well worth acquiring, even if you decide to skip Scelsi on subsequent playings.