Whereas Jazz had always been based on the concept of improvising over a chord sequence that was clearly in a major or minor, or blues-style key, musicians — in their constant search for new sounds — started experimenting with modes. Put simply, modes can be described as the scales you get if you start a major scale on a note other than the traditional starting note. So, in the key of C major, if you start your scale on the second note — D — you get a progression of notes that has a different sound from the one that starts on C. It has a minor feel, and is called the Dorian mode.