If the progress bar at the top of the iTunes window is moving, but you don’t hear anything:

• If you’re trying to listen to music through your computer’s built-in speakers, make sure the volume control at the top of the iTunes window isn’t turned down, and that your computer’s volume isn’t turned down (choose Apple menu > System Preferences, and click Sound).

• If you’re trying to listen to music through powered speakers connected to your computer, make sure the powered speakers are properly plugged into your computer’s audio port, plugged into a power source, and turned on. Also make sure their volume isn’t turned down.

• If you’re using remote speakers and the iTunes volume control is dimmed, make sure Computer is selected in the pop-up menu at the bottom of the iTunes window, and that “Disable iTunes volume control for remote speakers” is not selected in the Devices pane of iTunes preferences.

• If you’re trying to listen to music through remote speakers using AirPort Express and “Disable iTunes volume control for remote speakers” is selected, make sure your remote speakers are selected in the pop-up menu at the bottom of the iTunes window, and that the volume control on the remote speakers isn’t turned down.

If you’re using an AirPort Express, you can find more troubleshooting information in the documentation that came with your AirPort Express, or at the AirPort Support website.

If you can’t play a song:

• If you can’t play a song purchased from the iTunes Store, you may have exceeded the number of computers on which you can play your purchases.

  Unless the song is an iTunes Plus version, you can play an iTunes Store purchase on up to five authorized computers. After you authorize five computers, you can’t play the songs on a sixth computer until you deauthorize one of the five authorized computers. (For instructions on deauthorizing a computer, see Authorize a computer to play iTunes Store purchases.)

  If the song is available as an iTunes Plus download, you may upgrade the song at the iTunes Store. For more information, see Usage rights for iTunes Store purchases.

• If you’re listening to a shared library or playlist, iTunes skips iTunes Store purchases if your computer hasn’t been authorized to play them. To listen to a purchased song in a shared library or playlist, double-click the song. If your computer isn’t authorized to play songs purchased by the person who is sharing the song, you’ll need to enter that person’s Apple or AOL account ID and password to hear the song. For more information, see Share your iTunes library.

• You might be trying to play an AAC file that was not created using iTunes or downloaded from the iTunes Store. Songs you download from the iTunes Store or import into your library using the AAC encoder are encoded using the new MPEG-4 AAC format, and play in iTunes and on your iPod, iPhone, and iPad. Other AAC files that you find on the Internet or elsewhere won’t play in iTunes. For more information, see Choose import settings or Save a copy of a song in a new file format.

• If you’re trying to play a song on a CD that you burned using iTunes, make sure the equipment on which you’re trying to play the CD is appropriate for the disc’s format. For example, if you burned a CD-RW disc, you can play it only on your computer and some newer CD players. If you burned an MP3 disc, it should work in your computer and on special MP3 CD players, but not on standard consumer audio CD players. You can’t play DVDs burned using iTunes on most consumer DVD players. For more information, see Disc burning overview.

• If you’re listening to a playlist that includes a song preview, the playlist stops after the song preview. Double-click the next song in the playlist to resume playing the rest of the playlist. A song preview in your Music library or a playlist has a Buy button next to it.