The legal way to download music is by paying for it and  there a few websites where songs can be downloaded for free, though with some limitations. Some of these websites are:
1. Limewire – not very safe, a firewall, anti virus and spyware remover should be installed on the computer before download songs through Limewire
2. Piolet.com – some users find it safe
3. Some band websites allow you to download a few songs for free
4. Pilotspeed (formerly Pilate)
5. Soulseek
6. Using the audio section of Dogpile and type in the name of the song wanted. They have many songs available for download
7. Other P2P (Peer to Peer) websites like Warez, Morpheus, Zultrax and Ares