SDL_Mixer gaps between music

I’m having an issue where I cannot get two music tracks to play one after the
other without a pause between the end of one and the start of another. That gap
is more pronounced with .mp3 or .wav files and less pronounced with .ogg but it
is a very audible gap which appears in all situations. Talking about 300 ms or
so.

I am using the MusicHook to detect the completion of one song and to begin the
next. Using this method with sound works just fine with no audible gap between
playing.

How should I achieve this effect so that smoothly playing game audio loops do
not jar against each-other?