"West Side Score-y" Pt. 3: Tri-tones...They're Everywhere!!

Part 3

It seemed appropriate that Part 3 of this series was about the tri-tone. Even if it weren't for this numerical match-up, a post about the tri-tone seems inevitable when writing about West Side Story. Bernstein throws them into the score like I throw chocolate chips into cookie dough (excessively, perhaps, but to great effect).

Part 1 addressed something I called the "Smush Chord," and
Part 2 explored Bernstein's rhythmic stuff.
Part 3 continues, below... (read on!)

The Tri-Tone

Literally meaning "three-tones," the tri-tone is the musical interval spanning the range of three whole steps (6 half steps). Since our octave is most typically divided into 12 half steps, the tri-tone represents the octave divided exactly in half. The sonic result is a jarring, highly dissonant sound—so dissonant that history has given it the sinister nickname "diabolus in musica" (the Devil in music).

(More about the tri-tone and other intervals here.)

Melodic Appearances

1. "Do" up to "fi." Of course, the best-known example of the tri-tone (at least, within the realm of West Side Story), is in "Maria." The interval, here appearing as an augmented 4th, is heard in the first two syllables: "Ma-ri..." 
2. "Cha-Cha"
3. "Cool" (pictured below)
4. Basically everywhere.

from "Cool" (C up to F#, an augumented 4th)

Harmonic Appearances

from "Prologue" [C major over F#] and [Eb major over A]

1. Polytonal-type chords (a la Petrushka), in which a major triad is coupled with a tone 6 half steps away from the root, appear in selections such as "Prologue" (pictured above), "The Rumble," "I Have a Love," and several scene changes. In fact, the very last musical sound heard in the show is one of these puppies, with C major up high, F# down below.
2. Major chords, with #4 (a.k.a. #11). These bright chords, which suggest the Lydian mode, can be found, among others, in "Prologue," "Jet Song," and "Gee, Officer Krupke" ("Dear...")
3. #ii°7 diminished chords (in 3rd inversion). Closely related to the previous chord, this one is just slightly crunchier in sound. It's featured most prominently in "Something's Coming."
4. Whole-tone spots: "Tonight" m. 37 (pictured below)
5. Again, basically everywhere.

Pitch inventory (F, G, A, B, C#) comprised of whole tones.
(Tri-tone appears on beat 2, between F and B.)

Conclusion

To sum up (clumsily, quickly), that there are tri-tones just about everywhere in West Side Story is perhaps "needless to say," but there, I said it.

Being such a grating interval, it certainly catches the ear, and the sound sticks with you. It's what helps make the lyrical "Maria" so beautiful ("Say it loud and there's music playing / Say it soft and it's almost like praying..."), and it's what makes the show's final chord so hauntingly dissonant.