Find a site which illegally distributes them. Or find unlicensed / authentically free music. Zune, by Microsoft, offers free songs every now and then. Be aware that illegally downloading music is wrong and you can be seriously fined if caught.
Or you can turn to the some popular YouTube downloader, such as MacX YouTube downloader to download favorite songs from YouTube, Vimeo, Vevo, Facebook, etc. The downloaded music must be kept to yourself, no commercial purpose ever.