EDITING MUSIC
Music editing is a gift which depends on your ability to feel the empathy music carries with respect to certain images and vice-versa.
You should generally open a movie with a piece of music that conveys the mood of the story. It may be the main theme of the music scored for the movie or an appropriate piece selected from a "canned " (pre-recorded) music library. Sometimes canned music works better than a poorly scored "original" composition.
I used to be a great proponent of scoring original music for movies; but, I usually had bad luck it seems every time I tried it. Until one day, a young composer set me straight. I kept pestering him to come up with something grand and no matter what he came up with, it wasn't "profound" enough. So, finally, frustrated he hissed at me, "Who's greater than Beethoven -- how many hours of music did his nine symphonies amount to?" I was stunned and couldn't reply. Sensing victory, he twisted the sword, "Twenty hours?" "I guess so...." "Well," he went on, "How do you expect me to compose a 90 minute symphony for you, I just came out of music school?"
Actually music is a lot easier to judge by the average person on hearing it, than for someone to master it as a musician and certainly as a movie composer! So I don't make unusual demands on composers anymore, especially since a film maker can't afford original music on low budget. The ASCAP (music union) fees preclude the use of orchestral music, performed for an original composition as a movie score, for movies under one $1,000,000.
If you have a capacity for music and can create, somehow, a good musical score for your movie, of course, by all means, this is the best possible scenario. You can't beat original music that works. It'll add tremendously to your film's production value to have music that's specially scored for your movie.
But regardless of the music that you select for your movie, you should try to make it work with your images, sequences, transitions and theme of your movie.
Don't just use music to "underscore" or as "transition," however. Only on rare occasions this can be justified. Instead work creatively with music: "marry it" to your story, "fuse it" with the texture of your character's dialogue and personalities, "blend it" with the atmosphere of the film's environments, "explode it" with your images, like a 4th of July fireworks celebration!
When music is used well, you remember it forever. I saw THE THREE FACES OF EVE as a kid in the fifties, but I still remember the jazzy score that accompanied the great acting of Joanne Woodward. Everything about the shift and nature of her character's schizophrenic actions were mirrored in that music. The saxophone pieces were fantastically effective in conveying the frolicking moods of her character!
Maurice Jarre has done some terrific scores for the David Lean movies. I mentioned DOCTOR ZHIVAGO before, but, I'm sure you have your favorites; what works works, music is easily judged because it's a language that we learn early and it seems to have no international boundaries!
Cut in music meticulously, since you don't want any "bumps," distortion or drop-outs. Put it on separate reels (music only) and lay "filler" (blank mag or film -- when you use film, be sure to splice the base side toward the sound head, because you don't want the picture emulsion to gum up the sound head and cause recording problems later.)