No melodic death metal isn't an oxymoron. Just listen to it soemtime. Yeah a lot of it is hard and powerful and often it will go into incredible melodies. Listen to Emperor, Dimmu Borgir, Hecate Enthroned, Opeth, Cradle, Nevermore, Children of Bodom, and lots of other bands. THese guys know what they're doing when it comes to melody. Very much classically influenced...and I don't know how much more melodic you can get thsan that...