The library is offering the service Freegal, which allows users to download three songs in mp3 file format each week from the library's website at https://carnegie.freegalmusic.com. The music you download is yours to keep.Freegal® Music is a free music service from your library. All you need is your library card number and your PIN, the last 4 digits of your phone number. Freegal offers download access to more than 8 million songs, including Sony Music’s catalog of legendary artists. In total the collection is comprised of music from over 28,000 labels with music that originates in over 80 countries. There is no software to download, and there are no digital rights management (DRM) restrictions.
From Freegal's FAQs:
How do I get the songs into iTunes?
The easiest thing to do is to download the files to your desktop or your music folder. Import the song into iTunes by either dragging the song into the window or importing it from the menu. Presto, the song is now added into your library with all album art! Next time you synch up, you will see that song in your music library.
How do I get the songs into Windows Media Player?
If the song does not open directly into Windows Media Player, simply launch Windows Media Player then click and drag the song into the Windows Media Player window or simply Select: File - Import File. To select multiple songs Select: File - Import Folder. Select the file(s) you wish to add then click OK. The song will now appear in your Windows Media Player library.