This app was mentioned in 5 comments, with an average of 2.20 upvotes
Pacing is definitely top for engagement. Recently I had a discussion about engagement in another Reddit board. Some players also want to point out that we don't all need to be fully engaged 100% of the time. It's okay to slip a little.
I develop an app on Android for music, loops, and sound effects to set ambiance. It helps with engagement too, I find. Players feel the mood more and are excited by the sound effects when something interesting is happening. It's free, so check it out: https://play.google.com/store/apps/details?id=com.highfantasysoundboard
I haven't had a chance to use this this yet in a game but i found this free soundboard app for android High fantasy Soundboard
This Android app is my favorite: https://play.google.com/store/apps/details?id=com.highfantasysoundboard
I'm biased though, I'm there developer XD
https://play.google.com/store/apps/details?id=com.highfantasysoundboard this is a seemingly abandoned but free soundboard that has some great sounds in it