Album Art

I saw nice album pictures on some screenshots, where can I add them?

Album art is added for all songs scanned and added to your music database, see Configuration > Music > Database

Or, you may manually add a folder.jpg image to your album folder in Windows. If such a file is detected by MediaPortal, it will be displayed as the album art when any song in that folder is playing.  Note, you will need to have each album stored in a separate folder.

Visualizations Full Screen

How do I switch to a full screen visualization when playing a song in MediaPortal?

Hit X or your full screen keyboard shortcut. On some remotes the red button is mapped to full screen as well. 

Changelog

Volume Levels

My music files have different volume levels, how can I avoid adjusting volume on every song change?

You could try Foobar 2000 as external player. It has an option called "Replay Gain". Scan your collection once, activate it in Foobar's configuration and enjoy seamless track changes. Hint: Change the default settings from ape tags to ID3v2.