Comment from the liner notes:

The one Evans original, N.Y.C.'s No Lark, is a reworking of the concepts developed in his 1958 "Peace Piece" and 1959 "Flamenco Sketches".* But instead of the ostinato pattern and extended improvisation over it having the relaxed feeling of the earlier tunes, the tension and despair evoked by the piece here are almost unbearable. The title, by the way, is an anagram of Sonny Clark, an outstanding pianist who had died of a heart attack less than a month before this recording was made. The drug problems he and Evans had in common give the title and the performance an especially ominous cast.

And the footnote (*) says:

"Peace Piece" was supposed to be an introduction to Leonard Bernstein's "Some Other Time", but Evans so enjoyed playing over the C-major ostinato pattern that he made a six-minute piece from the introduction. Miles Davis heard the piece (according to Evans in a 1980 interview in Klacto) and asked the pianist to bring it to the studio:

I said, "Well, okay, but let's not do just one key level. Let's find, maybe, a succession of keys that we can go through and make a kind of logical circle." So we then chose the succession of keys for "Flamenco Sketches". ... So I would say "Flamenco Sketches" is half mine... Why Miles did that [claimed total authorship] I don't quite know...

Listening to "N.Y.C.'s No Lark" reveals that Evans uses the same type of ostinato but with a minor instead of a major tonality, which changes the mood entirely from "Peace Piece". Like "Flamenco Sketches", he doesn't stay on one key level.

I want to highlight the "circle" concept above. If you'll recall, I last wrote about "Flamenco Sketches" and its relation to Labradford, and the stasis that seems to make up lots of good ambient music.

Likewise, I've been thinking about circles lately. ("Y'know - for kids!") Part of the appeal of funk (I'm thinking here of late 60s James Brown) is its circular nature. Now, if you don't want to be charitable you can characterize music like funk, specifically the sort that vamps over one chord, or modal music, which sits on a single scale or set of scales, as harmonically "simple" compared to music done more in the Western harmonic tradition, or even something more contemporary to the two like bop, which certainly partook strongly of that tradition. I think this does a disservice to the implied (or sometimes explicit) circular structure of music of this sort, though. There's something special about a James Brown funk number in that it seems as if it need never end - and you don't really want it to, either. A lot of the modal pieces from Miles' modal period, and from Kind of Blue especially, have this quality to them. It's from this, I think, that the songs that have it most derive their quality of "stasis".

Fittingly, then, since it's based on the same structure as "Flamenco Sketches", "N.Y.C.'s No Lark" works well as a piece of circular music. Throughout, because of the underlying ostinato (mostly on lower piano keys), which is similar to that in "Sketches", there's a sense of motionlessness, or at least measuredness. But because the scales making up the ostinato modulate slowly over the course of the five or six minutes of the song, there's a slower, more drawn-out sense of motion than in a typical song.

I've been listening to "N.Y.C.'s No Lark" on repeat for at least a couple of hours - I'm having trouble remembering when I started. I don't look at the timer and I haven't been listening exactingly, so I can't even tell you where it starts and where it ends. But when joined in a circle, those two points coincide - which is just the point of the structure.