Please don't cross-post. With duplicate threads, anyone who tries helping out in one thread may not realise that someone may have already provided the answer in the other thread.
Probably the simplest way would be to embed a media player to play them and disable the right-mouse button. Most websites that don't allow saving of text, images, etc.. typically disable the right-click button. See this page for some info on streaming MP3s on a website and this page for info on how to disable the right-click button on the page.
This will stop most inexperienced users from downloading the tracks. Unfortunately, there's no effective way to totally stop advanced users from being able to download tracks, since there are a wide range of tools available to download streaming tracks and videos, even from major websites such as Yahoo Music and YouTube.