I feel so discouraged... I picked up David L Burge relative pitch course and I'm just so stuck on harmonic intervals between 4th's and 5th's. I'm fine with the melodic intervals, those come through as clear as can be, but I just can't seem to consistently hear the difference between a harmonic 4th and a harmonic 5th. I've tried singing just those specific intervals in many different kind of ways, it just seems that there is no way to do this. It's been over a week now and I'm still stuck on this part. Has anybody else struggled immensely with this part of ear training as I am and what did you do to overcome it?