Thanks for your reply!
A license is free as long as your project is non-commercial or an indie title with a budget of less than $100k. I was going for that, like I would have done for Unity or Unreal 4, but if for Visionaire only the devs can do it, I guess the licensing would be quite costly.
Effect modules would be great, though the reason I'm looking to FMOD is primarily for the opportunity to have dynamic music
I tried to mimic having several channels using action events, using pause events and checking if conditions had changed when the pause was finished, etc, but it always came out of synch. The solution that works the best so far is to change the background music at various intervals, and hope the seams are not too obvious. Not perfect, but at least it's dynamic in terms of time if not in content.