A very difficult theme to talk about. Everyone knows irish - or scottish - or even bretonic music, but what the hell is german music? Forget about those songs in the charts - they're plastic products as everywhere in the so called western world. Forget about songs in "Musikantenstadl" and similar TV-series - they just claim to be folk music, but they aren't. And traditional? Tradition in Germany has been severly cut according to the effects of WW II.
So, what remains?
Some of the german songwriters delevoped styles of their own - Reinhard Mey or Hannes Wader, for example, the latter never being really popular. Some picked up the international type of Rock Music and changed it to fit german tongues - Udo Lindenberg is one of them. And many, many unknown choose the celtic tradition rather than the german one to build upon.
German music, in conclusion, is a wide spread scene with some sparkling jewels. Just try and listen.