Judi Dench might give yet another brilliant performance in Notes on a Scandal, and Cate Blanchett might be equally praiseworthy. The movie as a whole might be a terrific tale of repressed longing warped into mental instability. All these things might be true, but I can’t know for sure, because I spent nearly the entirety of its running time preoccupied with one question: What combination of cash, threatening and pleading would it take to get Philip Glass never ever to write another movie score?

I can’t speak for director Richard Eyre, but I’m guessing that’s not the reaction he was looking for. Typically, you want your movie’s music to set a tone while remaining relatively unobtrusive—a harmony that complements the melody of the narrative and performances, rather than a dissonant counterpoint that overwhelms them. Yet for 90-some-odd minutes, Glass’ excruciating orchestrations kept turning even the simplest scenes into lurid melodrama. It was the auditory equivalent of trying to read a book while someone keeps flicking you repeatedly in the back of the head.

Screenwriter Patrick Marber’s adaptation of Zoë Heller’s What Was She Thinking?: Notes on a Scandal, begins at a North London school, where veteran history instructor Barbara Covett (Dench) is beginning yet another term teaching working-class teens she can barely tolerate. Into her world comes Sheba Hart (Blanchett), beginning her first year teaching art and struggling to get her bearings after years as a stay-at-home housewife and mom to her special-needs son. Barbara offers to be the anxious Sheba’s friend, an offer Sheba gladly accepts. But Barbara’s attentions begin to grow a bit too attentive—especially after she discovers that Sheba has been carrying on an affair with one of her students (Andrew Simpson).

Marber employs Heller’s structure of Barbara’s diary entries as our point of entry into the story, and he creates a firm foundation in his judicious use of voice-over. It becomes evident soon enough that Barbara has lived her entire life in the deepest possible sexual-identity closet, her few awkward attempts at establishing connections with other women turning into borderline obsession. There’s a slick decision at one crucial point to slide from what had been a story told entirely from Barbara’s perspective to one where we see key events of which Barbara is unaware. All in all, it’s smartly structured and full of promising thematic material.

Oh, and it has Judi Dench. There’s a school of thought that Dench only plays variations on the same tough, imperious theme—her “M” from the Bond films is her Queen Elizabeth from Shakespeare in Love, etc. But it seems here that she understands that perception, and plays her creation of Barbara against it. Yes, she’s the kind of flinty teacher who can freeze a classroom in its tracks with a glance. She’s also so clearly desperately lonely that her misanthropic journal jottings become the wall she raises between herself and other people. Dench does her finest to create a character that is more than a compendium of psychological clichés.

And then there are those head-flicks that are every note in Philip Glass’s score. Any chance there was at finding a complex, even sympathetic side to Barbara’s manipulations is crushed by musical cues so bent on ratcheting up the “isn’t this all very ominous and threatening?!?!” quotient that they steamroll the character interactions. The fundamental rule of suspense is “build and release,” but Glass’s approach is more along the lines of “build and build and build and build,” so that every walk up a staircase is greeted by a flurry of portentous arpeggios, and every low-key conversation warrants a creepy crescendo.

It’s a fun exercise in dissecting the art of filmmaking to watch a movie like Notes on a Scandal and imagine what it would be like with literally no music at all. Contemplate how what seems on the surface like a tabloid premise could be rendered subtle and insinuating. Imagine what it would be like not to receive musical nudges in the ribs telling you that at any given moment Judi Dench may be about to boil a pet bunny. An intriguing character drama is lurking somewhere beneath Glass’ bombast, which keeps telling you you’re watching Lesbian Stalker from Hell.

NOTES ON A SCANDAL

**1/2 (two and a half out of four stars)

Starring: Judi Dench, Cate Blanchett, Andrew Simpson.

Directed by Richard Eyre

Rated R.