Crossfade
Crossfade between two tracks during track transitions. The end result is a smooth transition similar to what a DJ does when changing tracks.
Auto Crossfade Duration
How many seconds the two tracks should play at the same time when GMMP automatically changes tracks. Situations where crossfade is applied by default is when GMMP transitions to the next track in the queue and it is not the next track in the playing album. The album and track number is used to determine this.
Replaygain
Replaygain will adjust the gain/volume of the playing track based off replaygain tags stored in the playing file.
Seek Time
Determines how many seconds to seek forward or backwards when the seek buttons or gesture actions are used.