I have created a project with narration on most slides and added background music. I can get the background music at the volume I want during the narration on each slide but when the narration stops, the background music level increases. How do I get the music level to be consistent across all slides? I'm in Captivate 2019
Go to Audio > Edit > Background and when the dialog appears, choose the Add/Replace tab. At the bottom of the dialog there is a slider to control the volume drop when narration audio is active. By default the background audio volume is set to drop by 50%. If you just want the background audio to be the same volume regardless, then set this slider to 100% volume and edit your background audio clip via the Library so that its normal volume is at the level you want.
The method that Captivate offers for controlling the background audio initially seems to be OK. But when you work with it you find there is one huge flaw. The background audio changes in volume instantly as soon as the narration audio starts up. The effect is very sudden and quite jarring on the listener. If Adobe's developers had only given this a little more thought they would have realised they needed an extra function on the dialog here to set the fade-in and fade-out timing of the volume changes. If they had done that, the effect would have been quite professional and smooth to the listener. As it is the volume changes become very annoying and I don't personally use background volume at all because of the way it's been implemented.