MGM went on a youth kick in the late 1950s under Sol Siegel, with sometimes effective results (Where the Boys Are), other times misfires (The Subterraneans). This falls in the latter category, with a script by Robert Thom who also wrote Subterraneans.
It's a weird thing of a movie - George Hamilton, who appears as the second male lead, described it accurately as a combination of Southern Gothic and a biopic of Chet Baker. There's lots of Southern accents and heaving bosums, and characters who just need sex, and get all tormented and act all over the place - the influence of Tennessee Williams. There's women talking about being horny and drink scenes and suicide attempts and death.
Natalie Wood is poor white trash in love with poor white trash Robert Wagner (tousled hair, top buttons of shirt undone) but they can't be together for some reason or another (this is a major weakness of the story) so Wood heads for the city where rich trash George Hamilton falls in love with her; Hamilton's trashy, horny sister Susan Kohner falls for Wagner.
The most surprising thing about the movie is Wagner's relationship with self-destructive singer Pearl Bailey - he seems to love her and she him, and they live together; the characters speak a lot of lines about "we don't do any more than that" but you could easily read miscegenation into it.
Natalie Wood acts her heart out and I bought her being in love with Wagner - but he seemed unable to convey the same passion for her. (To be fair, the script doesn't help him - if he really wanted her he should have been with her). Wagner's trumpet playing is fairly convincing and Hamilton was surprisingly sympathetic as the well-off-but-basically decent rich kid who gets in over his head. Kohner over-acts. Pearl Bailey's part needed to be much bigger.
The plot about Wagner being a top jazz musician doesn't seem to go anywhere. (He seems to be able to play the trumpet awfully easily without practising.) There's a funeral at the end for Pearl Bailey which feels like a rip off of Imitation of Life. And the ending feels super convenient - Hamilton just happens to fall in love with Kohner and Wood with Hamilton, and we haven't seen any of it when for most of the film there's meant to have been this big Wood/Wagner passion. It's a mess of a story. It's interesting, but a mess.