Music differences between animation and live-action?

I don't see a great difference as far as the score is concerned. Music for animated features can, according to the mood of the scene it's supposed to underline, be as varied as for live-action movies.
There are many examples in which a score sounds goofier or has a rhythm more explicitly timed to the beat of the animation to help emphasize the action. A negative example for that, to my mind, is the use of music in the Warner Bros. shows of the 90s, like Animaniacs and Freakazoid!, in which practically every gesture and pose change got its own chord. I thought the soundtracks were rather unmelodical because they didn't follow their own pace; they were just harmonical tunes glued to onscreen action which in itself was an accumulation of poses, not a seamless flow.
Same with sound effects, although I must admit that many modern productions grate on my nerves with their constant audio overstatements of onscreen actions. A character zipping offscreen will be accompanied by the sound of a firing gun in 70% of the cases.

Great topic.

There's a book called "Film Music" by Roy Prendergast which has an indepth chapter on "cartoon music". It's from the '70s and he uses classic studio films as examples.

A few things lead to different approaches to scoring animation.

First, there's no natural room tone or base audio. If I'm on film typing, the audio will be picked up. Now that can be replaced entirely with Foley effects, turned off or kept as is -but at least something is there.

In an animated film, the picture is physically independent of the audio. Draw me typing, and no matter how skilled you are, the drawing exists as a visual only.

Second, animation -for the worse -it typically cartoon. It's exaggerated. Why is this? As we know, it's to give the action weight and to make it seem real.

But it's not "real". Sound design is going to further emphasize the action. If I'm tip toeing, we might have delicate string plucks for my footsteps. This helps emphasize the action and clarify the acting.

There is also the notion of verfremdungseffekt which is key to animation in ways film and theater performance never could be. Familiarize yourself with Brecht's "Notes on the Opera Mahagonny" and his analysis of music there and you'll gain great insight into music and performance for the animated film.

You should also be fully familiar with Neitzsche's "Birth of Tragedy". To fully appreciate that you should revisit "The Poetics" of Aristotle.

I don't see a great difference as far as the score is concerned. Music for animated features can, according to the mood of the scene it's supposed to underline, be as varied as for live-action movies.
There are many examples in which a score sounds goofier or has a rhythm more explicitly timed to the beat of the animation to help emphasize the action. A negative example for that, to my mind, is the use of music in the Warner Bros. shows of the 90s, like Animaniacs and Freakazoid!, in which practically every gesture and pose change got its own chord. I thought the soundtracks were rather unmelodical because they didn't follow their own pace; they were just harmonical tunes glued to onscreen action which in itself was an accumulation of poses, not a seamless flow.
Same with sound effects, although I must admit that many modern productions grate on my nerves with their constant audio overstatements of onscreen actions. A character zipping offscreen will be accompanied by the sound of a firing gun in 70% of the cases.

I couldn't agree more about the 90's WB cartoons. It also sort of made the shows feel more juvenile and silly than they were, and it often seemed forced to me.
For instance, in Pinky and the Brain, they'd have some adult satire of a well-known politician, and they'd have Looney Tunes-style music underneath it, which felt really out of place. Another thing that bugged me was that they'd always use the exact same sound whenever anybody got hit by anything heavy...But I'm kinda getting off-topic.

Check out Hans Perk's Blog, it details how the animation in old Disney shorts was timed to the beat of the music. It has some great resources including millions of bar sheets, a beatronome, an essay on "The Relation of Music to Animation" and links to a book on Disney's Music.