5. What is the function of the M15's Multifunctional Button?

With the Multifunctional Button, you can quickly achieve a specific action with just one click. By default, it's used to add the currently played track to the Favorites list while using the FiiO Music app. But you can specify a different function to it in Settings -> General -> Multifunctional button. Currently the available functions are: Add to Favorites, Play next randomly, Delete the currently playing song, Switch filter, Switch equalizer, Enter USB DAC mode, Enter Bluetooth receiving mode. And we will also add more functions in the future.