Standard Mac or DOS MIDI files can be imported to a movie and played back in a variety of Mac multimedia programs. Library rates depend on how the publisher chooses to do business, and how you plan to use the music. But they're surprisingly consistent. You don't pay any more than the disk fee, until you've decided to use a particular piece. But the only limit is your creativity.
Annual blankets are also available from the needle-down houses.
You pay a fixed annual fee for everything you produce that year, and they usually throw in the disks for free. Prices vary widely depending on the size of the library. As with production blankets, bigger publishers' licenses are worth more because the music selection is wider. Buy-out libraries sell you the disks and licenses simultaneously. Almost all the publishers give discounts for multi-disk sales.