Do a google search for these. If you use DC++, tell me and I'll rip a couple of these for you. So: anything by Hesperion XXI and Jordi Savall (a performing ensemble and its conductor), Ton Koopman's Bach organ works, Gesualdo: Motets and Responsories, Palestrina, Lassus and De Victoria. I'm not sure if you meant modern bands with an 'ancient' theme, but there's nothing better than the original thing.