First, go to settings->Global->Playback and turn on System volume slider control.
An alert will appear telling you to quit unrealBook manually. This is needed to enable the feature.
Go to the CD/Music menu and choose Music Controller.
Press Link Audio File (in Blue).
Choose the mp3 (or mp4) song you want to link to the page. You can use the search field to find the file. Press the title to select the song.
Next, go into the CD/Music menu again and choose Player Volume.
Set the slider to the volume you want for this song and then press Set Volume For Page.
Now when you choose this file and turn to the page and press play, the file will play at the predefined volume. Once a volume level has been saved, the window will display the volume level saved with the page.
Choose Play iTunes Song access your iTunes Music Library.
Choose between your Playlists, Artists, Albums or Songs. Select a song to play by pressing it. The song should start playing.
Press the Back button on the top left to go back to the Music Controller.
Press the link icon in the Music Controller to link the currently playing song to the PDF. Note that you can link a different song to each page of a PDF. Every song that you link should have a name and artist defined in iTunes.
Press the Music Button to access the Music Player controller to control playback and link a song in your iTunes library to a PDF file.
The Music Controller will control the playback of any songs linked to the current PDF. The -4 and +4 buttons will allow you to skip forward and backwards by 4 seconds. The slider will allow you to jump to any point of the song. The Start offset will allow you to start from a predetermined point from the beginning in seconds.