To use Music Speed Changer with Dolby Atmos, turn off ‘Use native audio library’ in settings.
Dolby Atmos
Dolby Atmos is a surround sound technology developed by Dolby Laboratories. It is used to create the feeling of being immersed in the atmosphere with use of complex surround sound by allowing sounds to be interpreted as three-dimensional objects with neither horizontal nor vertical limitations.
Dolby Atmos implementation in phones use a dual loudspeaker virtual surround sound implementation, similar to that used in Dolby Atmos TVs and Soundbars, as well as binaural headphone technology.
Turning off ‘Use native audio library’
Open the Player Main Menu

Select Settings

Scroll down and select Advanced

Uncheck Use native audio library

That's it! You can now enjoy Dolby Atmos immersive surround sound using Music Speed Changer.