If you are experiencing audio problems when using the LUMI app, the best way of improving the audio performance of the app is by deactivating Speed Control and Enhanced Audio in App Settings.
How to deactivate audio features
Open the app, and tap the Achievements symbol in the bottom-right corner.
This will take you to Your profile.
Scroll down (iPhone/Android) or across (iPad) to Settings and tap App Settings.
Tap the sliders to toggle Speed Control and/or Enhanced Audio on or off.