The searches for "free mp3 downloads" is 26047 a day while for "free mp3 download" is 2131 a day. Big difference. The reason it "doesn't" work is because "free mp3 download" does not have "129,620" searches on Overture. Most of these Overture searches belong to "free mp3 downloads". Overture does not tell the singular and plural apart, it simply adds them together. And this is not the first time I have seen someone excited over the Overture searches for their new domain when they had the wrong tense.
This is the reason I like to use Wordtracker
to evaluate domains as opposed to Overture. I did the above with the free version.
Another thing to consider here is .ogg. This format is open source, and provides better sound quality than mp3, and has a strong potential to become the defacto standard in the future. They have just come out with version 1.0 So mp3 domains may not be as attractive in the future as they are now.
By the way I just regged freeoggdownloads.com. Please note the s