For the past half year I have been learning to play soprano on yanagisawa s901. My main instrument is the alto (yamaha YAS62II) which I have played for 1 year. I however am having problem with response on low G and down. The mouthpiece is an yanagisawa HR #7 (stock), and I get a shaking tone when I blow the low register vigorously, the situation become slightly better when I change the mouthpiece to yamaha 4C, but the problem still exists. If you have any information of ideas on how to improve my response in the low register, it would be very appreciated. BTW it's my first thread. Thank you.