Find the "most recent" sample playing in a group of channels.
int Mix_GroupNewer(int tag);
an arbitrary value, assigned to channels, to search through.
Returns the "most recent" sample playing in a group of channels
Specifically, this function returns the channel number that is assigned the specified tag, is currently playing, and has the highest start time, based on the value of SDL_GetTicks() when the channel started playing.
If no channel with this tag is currently playing, this function returns -1.
This function is available since SDL_mixer 2.0.0.