When it comes to judging the year's best movie music, what is it that makes an in-film song pop? Is it keen placement? A sweeping symphony? Star power? A memorable hook? Relentless repetition?

Those certainly don't hurt. But when you look at the many nominated tunes since the best original song category's creation in 1934, one connection is increasingly obvious in the hits that clicked.

A successful song must be intrinsically attached to the film. It must align itself aesthetically with the film. It must define the film.

True definition means that you can't think about that film without humming the associated tune — or at least hearing it in your head.

Successful songwriters and filmmakers are going for a psychic connection, and sometimes they achieve it. Remember Eminem's acting debut in 8 Mile? Try thinking about it without reliving his infectious hit "Lose Yourself," which recently helped score the Motor City's Super Bowl commercial for Chrysler. Singularly, the song and the film were successful; together, they were genius.

You may not be familiar with the 1969 comedy A Hole in the Head, but you've probably heard its Frank Sinatra hit "High Hopes." And Butch Cassidy and the Sundance Kid? It's all about Butch (Paul Newman) taking Etta (Katharine Ross) for a bicycle ride to the tune of "Raindrops Keep Falling on My Head."

We don't even need to get into Titanic or Dirty Dancing, as those "My Heart Will Go On" and "(I've Had) The Time of My Life" moments are still burned into our collective memories.

Like the above songs or not, their placement in film won them all Oscars — and more important, they succeeded in their goal of summing up an entire film experience in four, musical minutes. Consider the challenge of wrapping up 120 emotional minutes in one-thirtieth of that time.

Of course that can be a simpler task when the movie is a musician's biopic — as in 8 Mile or Crazy Heart, the latter of which won the original-song award last year. Even then, you still need a spectacular song, especially if an audience is expected to feel the gravity of the moment and buy into the on-screen musician's talents.

For example, this year's Gwyneth Paltrow vehicle, Country Strong, is nominated in the category for its "Coming Home." The pop-country jam is easy on the ears, but it's hardly memorable — mostly due to the film's laughable depiction of a past-her-prime country singer battling alcoholism and other demons.

As they often are, this year's original-song contenders are largely forgettable. "If I Rise" is a slinky, down-tempo number from 127 Hours. The song's primary songwriter, A.R. Rahman, won the same award a few years ago for his exuberant "Jai Ho" in Slumdog Millionaire, but this song — featuring Dido on vocals — is hardly the kind of song you'd leave the theater humming.

"I See the Light" is another ballad, though its source material — Disney's 50th animated film, Tangled — is home to stronger songs. "We Belong Together" is this year's seemingly obligatory nomination for Randy Newman, who wrote the lazily upbeat song for Toy Story 3.

Is it surprising that three of this year's four nominated songwriters already have original-song Oscars on their mantles? (Rahman and Newman each have one, and "I See the Light" author Alan Menken owns eight Oscars — four of which are for original song — from his 20 nominations.) No, it's an insider's game.

And given the constrictions and expectations placed on these songwriters and musicians, it's easy to see why these hired guns are so successful and omnipresent.

First Published February 28, 2011, 1:41 a.m.