For anyone getting started with FMOD & Unity, I’ve just put together a Unity package to help you with FMOD callbacks - particularly useful for rhythm games/mechanics or games that have behaviour tied to music and sound effects.
Free to download and use, you just have to add the FMOD package (from the asset store) to the project. Currently working with Unity 2019!
I hope to keep working on this and create something really solid that makes integrating with Unity and FMOD much simpler than it currently is, especially for solo/indie devs, or those without strong programming backgrounds.