The Hernando County Library provides the ability to download a few mp3 songs each week. These songs are yours to keep forever. This is through an app on your phone Freegal or via their web site http://hcpl.freegalmusic.com. If you know your library card number and your pin, you can use this service and start building a collection of songs today.
Freegal says they provide access to the Sony Music catalog along with around 28,000 smaller labels. They state that they have more than 11 million songs available, but that the number changes daily. A couple of year ago they only had 8 million songs available.
The files that you download are yours to keep and are standard MP3s without any special Digital Right Management (DRM), so you can play them on anything that can read an MP3. Many other services will only allow you to play what you purchase on their service. You can load the DRM free songs on your phone, computer, etc. and enjoy them whenever you want.
You can see the number of downloads you have remaining for the week. When the number of downloads remaining hits zero you only have to wait until the next week begins to download more songs.
If you are looking for music, it is a good idea to check freegal first. You may not need to purchase the song.