"The experience of a film is immersive and music is supposed to underline and help that experience," he told BBC Radio 3's In Tune.
"If you notice it, maybe its working too hard, or maybe it's too loud. It's all very delicate in the end."
The US composer, who premiered part of the Spectre score on BBC Radio 3, said working on the film has been "tough".
"It was a lot of hard work," he told Sean Rafferty. "I've been at it for three-and-a-half months solid. Seven days a week, morning til night. There were tough moments but all in all, it's strong and I feel good about it."
Newman's first Bond score was for 2012's Skyfall - the highest-grossing Bond film of all time.
He said the project had been daunting "because I'd really never scored an action movie".
Pressed for details about the latest Bond film - and how the music complements the action - the composer remained tight-lipped.
"You're not supposed to give anything away," he said. "It's crazy. It's not that I even want to talk about it, or not talk about, I just know that I shouldn't."
The 12-time Oscar nominee has previously worked on the likes of The Shawshank Redemption, American Beauty and Finding Nemo.
He played a bombastic, pounding clip of his Spectre score on Radio 3, taken from a sequence set in Rome.
Preview clips suggest the piece could soundtrack a set-piece "cat-and-mouse" car chase through the city, but Newman refused to be drawn on the details.
"It takes place in Rome. It's very fast-paced," he said. "I can't tell you about the type of cars but there are cars. There are roads that the cars drive on, as well.
"I won't say anything because I don't know if I'm supposed to or not."
Bond composer Thomas Newman says movie scores should be unobtrusive, otherwise they upset the balance of the film.