I've spent a lot of the last few weeks listening to movies. It's easy to forget that movies are as much about sound as they are about the visuals. Obviously you expect things that happen on-screen to make some sort of noise - you expect guns to go bang, slamming doors to make a big crash, and so on - so I've been working out which of our animations need sound. Actually, it isn't as simple as it seems. Soundscapes in movies are completely artificial, and vary rarely reflect the actual on-set sound. If everything made a sound that actually does make a sound in real life, you'd end up with a real mess. What you have to do is to ensure that things which are interesting or significant make a sound, and unimportant things don't. This, of course, varies from movie to movie. In Kurosawa's Throne of Blood, there's a fantastic scene where the only sound is the rustle of a silk kimono; most of the time, you don't hear most of the clothing noises. Sometimes you want chairs to squeak when you sit on them, at other times, you need them to be silent so you don't cover up the dialogue. It's quite an art choosing which sounds you're going to carry through from the footage to the soundtrack.
One issue we've been thinking about is whether we should supply noises for characters such as coughs, sniffs, sobs, and so on. You could do them as a "say" and record the sound yourself, and as a result, the voice tone will always match; if you've got a character with a deep bass voice, you don't want a high-pitched cough, which is a risk you run with pre-generated human sounds. On the other hand, it does mean you have to record all the sounds, try to make the sound match with the animation, and the lip synch gets confused. We're going to try getting a few sample sounds in, see how well they work when combined with different people's voices, see what feedback we get from users, and get some more if it seems like a sensible way to go.
However, where sound really comes into its own is where it adds things to the film that aren't on the screen. You can use sound just to add atmosphere, or you can use a sound to portray an event that you can't (or don't want to) show on screen. As a simple example, you have a scene set in a house. You then hear a car crash outside, and the characters rush out to see what's happening. And there's the old low-budget standby: film a scene with a few extras in, choose your character angles nicely, add some crowd sounds, and it feels like you have a much bigger cast. As a result, I've been choosing a load of "generally useful sounds" that we can just add in to movies to cover some of the things we can't quite do yet.
I'm also planning to commission some cartoon-type sound effects, boings, and the like, because you never know when they're going to be useful. A silly sound can turn an otherwise straightforward animation or facial expression into a priceless comedy moment. I'm also thinking we should have a few music clips: nothing too long, just little moments, such as the signature tune for a games show (think Millionaire), or a classic "spooky moment" and the like.
Anyway, given that little lot, you should be able to create interesting sounds for your movies: Moviestorm will have dialogue, ambient noise, sound created automatically by the animations, various sound effects you can add in at will, and of course you can add your own music tracks or sound effects.