Place the song files in this directory.  It accepts .MP3 files, and .SNG files.
To make them work together, you need to make sure that the filename in 
the .sng matches exactly the filename of the .mp3 file.

One way to do this is open up the .sng file, and change the filename to make
them match.  The other way is to open up the .sng file and rename the 
.mp3 file to match.

Example:

<Song>
    <Properties>
        <Version>0.1</Version>
        <Title>Hate You.mp3</Title>
        <Artist>No Artist Set</Artist>
        <Album>No Album Set</Album>
        <Year>0</Year>
        <BeatsPerSecond>16.0</BeatsPerSecond>
        <AllowableErrorTime>0.25</AllowableErrorTime>
        <Length>187.794</Length>
        <MusicFileName>Hate You.mp3</MusicFileName>
        [...rest of the file deleted...]

The MusicFileName is "Hate You.mp3", so it looks for a file by that name.

