Hi,
What version of Unity and FMOD are you using? Could I get a screenshot of the event in FMOD Studio?
An option could be using Transceivers (FMOD API | Event Reference). Begin with the Source Event we will want to set up Audio Tracks (FMOD Studio | Glossary) for each of the tracks e.g. lead, bass and drums which will have their own transceiver sending to a receiver event. Finally make sure the Master Track on the source event has its Fader set to -80dB, this way it can be added to the Unity scene but won’t be heard.
Each
receiver event will need need to have a small Loop Region (FMOD Studio | Glossary) to keep it playing to receive the signal from the source event. Also adding a Spatializer will allow for the attenuation and panning you are looking for.
Now you can have the source event playing in the scene and each of the receiver events playing their signal from their position in the world all while staying in sync. Hope this helps!