I’ve tried to pick some of the melodies and accompaniment out on the piano, and discover that, playing the melody to one, I’m also playing the accompaniment to the other. Sondheim, a puzzle-lover and a trained composer, likes to cross-reference bits of songs this way.

For instance:

– the main theme played so loudly in the opening credits is hundreds of years old, going to the words “Dies Irae, Dies Illae” (“Day of wrath, day of mourning”) of the ancient Catholic requiem.

– The same pattern of notes, played rapidly and softly (in musical terms, an “ostinato” because it’s stubborn or “obstinate!”) then altered a bit, show up often in the score (associated with the phrase, “There’s a hole in the world like a great black pit,” and with Mrs. Lovett’s song “Wait”).

– While that same pattern plays in the low strings during the opening title, we hear some wind instruments play a counter melody above — and that becomes the second phrase that Sweeney sings in the movie: “Life has been kind to you,” and appears all the way through the movie. The melody that fits over those becomes, “There was a barber and his wife. . .”

– and the notes for the words “There was a barber and his wife” also begin each phrase of Sweeney’s lovely melody where the movie is most gross, a song called “Johanna,” when he sings, “And are you beautiful and pale . . . Johanna?” though the melody turns in another direction.

So maybe Depp meant “angular?” “Obscure” (in the sense of dark)?
“Ostinator?” All of these: but not obtuse!