If like me you and your friends/band members all have similar tastes in music and your cd/mp3 collection is so similar they could be called twins so their no help to you.  I suppose you could listen to the radio but that doesn’t help you find some of the great bands that are not so radio friendly. 

Luckily your not alone some others marek gibney faced a similar problem and came up with Gnoosic.

Gnoosic

It’s a simple concept really you provide the site with 3 bands that you already know and like and it will go through and suggest other bands that you may like, and then for each one you select whether you like, dislike or do not know them.  Then when you’ve done this for all the suggestions you are taken to a summary so that you can research the suggested bands.

The greatest strength of this system is that the more people that use it, the more accurate it becomes as it begins to build relationships between the suggested bands and whether people like or dislike them, essentially learning from peoples tastes.

The system has also been employed for books (Gnooks) and movies (Gnovies)