• If you’re using 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 using powered speakers connected to your computer: Make sure the powered speakers are properly plugged in to 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 AirPlay pop-up menu at the top of the iTunes window. Then choose iTunes > Preferences, click Devices, and make sure “Allow iTunes audio control from remote speakers” is not selected.

• If you’re trying to listen to music through remote speakers using AirPort Express: Make sure the remote speakers are selected in the AirPlay pop-up menu at the top of the iTunes window. If you only want to use the volume control on the speakers, choose iTunes > Preferences, click Devices, and select “Allow iTunes audio control from remote speakers.” Make sure the volume control on the 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 purchased from the iTunes Store: You may have exceeded the number of computers on which you can play your purchases.

  If the song isn’t an iTunes Plus version, you can play it 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 can 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 iTunes libraries on a local network.

• If you’re 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.

• You might have exceeded the number of computers authorized to play the audiobook.

  Audiobooks purchased from the iTunes Store can be played on up to five computers at a time. The computers must be authorized to play purchases from the iTunes Store. (You can’t play these files on a sixth computer until you deauthorize one of the already authorized computers.)

  Audiobooks purchased from the Audible website can be downloaded to up to three computers at a time. The computers must be authorized to play purchases from Audible.

  To see where an audiobook was purchased, select it, choose File > Get Info, and then look in the Kind field. Files purchased from the iTunes Store end in “.m4b.” Files purchased from the Audible website end in “.aa” or “.aax.”

• You might be trying to listen to an Audible file that was purchased using someone else’s account.

  To see who downloaded an Audible file, select it in the library and choose File > Get Info. The Purchased By or Owner field shows the user name for the account holder who downloaded the file.