Hold your breath

Schoenberg, in his Fundamentals of Musical Composition, the small book in which he gets most clearly down to practical issues of form and his own stylistic tradition, identifies the phrase as the "smallest structural unit"  (he calls it "a kind of musical molecule", thus implicitly putting the single tone or note (i.e. the things we count when we count to 12 tones (as one supposedly does when practicing a famous method of composition associated widely with Schoenberg's name)) at a kind of atomic level.)  More interesting, to me, is his defining the structural meaning of the phrase as "a unit approximating to what one could sing in a single breath."  This is very concrete and naturalistic as a definition and immediately gives the phrase, as a unit consuming some amount of time, both a certain range of duration and an implicit shape.  Range: a breath can be short or long, regular or irregular, you can lose your breath, temporarily or altogether. An asthmatic (like Schoenberg himself) might well find his or her music marked by sudden stoppages and shortnesses of breath (see episodes of Schoenberg's String Trio or the rapid patter in parts of Pierrot Lunaire.)  But at the same time, once you begin with breath as part of your premise, there is always the dialectical potential of breathlessness, non-stopping. Stravinsky damned the organ for never breathing, but traditionally, it's been the perpetual motion of the violin that has been associated with the diabolical. And shape:  the phrase has to begin (obviously) and sometimes does so with signals, like pick-ups, and though it be the "smallest structural unit", it usually has an ending too, like a bit of punctuation (typically ,-ish, but also ?-ish, !-sh, or .-ish (I happen to like ;-ish or :-ish, such that the next phrase complements or explains/disambiguates the first) which could be rhythmic, either strong or weak, or pitch, often a falling off, Schoenberg noting the use of smaller intervals and fewer notes (or, as we'd say, a decline in density of activity (i.e. we're out-of-breath.)   All of this, so far, could be useful in any kind of music with tones, but Schoenberg identifies some features that are distinctive to his own tonal-harmonic tradition, specifically that the phrase typically outlines a single harmony or a simple succession of harmonies (it is worth noting that Schoenberg, already in this "smallest structural unit" for a traditional tonal music finds himself using a linear expansion of a vertical sonority (or vice versa), a central premise of his own (much of it, post-common-practice-tonal) music) and that this outline is typically drawn from a small handful of techniques: arpeggiation, adding upbeats, altering rhythmic values, adding passing tones, appoggiaturas and cambiati, adding repetitions of tones, and ornamenting. So far so good. (You may exhale.)