At this time I'm suffering from dirty notes or a double buzz. I have returned to basics, but this seems to be a particularly persistent problem this time. If I play quite softly my tone is fair and clear of the nasty sound. If I get louder, around MF it returns and is persistent. I am sure I can overcome this but it is taking longer than usual. What is the cause? Tired muscles, poor or stretched lip tone. What? And any info to help recovery. I have been playing softly, doing long tones and slurs and generally takin it easy. I seemed to be recovering, played a rehearsal and seemed to relapse. Any ideas.