i've been wondering, i can sweep pick rougly, but for some reason I can't mute cleanly the f**** G string. let's say i'm playing this:


as soon as I change my fingers and press down on G9 there's a buzzing sound. before i even pick the string it buzzes.

how can i avoid that and mute properly?
it could be normal fret buzz, in which case you might have to adjust your action a bit. If you can't hear it through the amp then I wouldn't worry about it though.

You might also need to either pick the G string faster or press down on the fret a little slower. If your timing is slightly off that could cause some excess sound.
could be making accidental contact with your picking hand. Just go through it slow to make sure your hand doesn't brush the string before your pick.
your picking hand may be touching the string before you pick it, depending on if you're anchoring your hand on the bridge or not. that's the only thing i can think of. it's probably just technique and will eventually go away with practice.
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Hey man, here you have a sweep picking tutorial : http://www.guitarlearningtips.org/guitar-technique/sweep-picking-exercises/ that i wrote a couple of weeks a go.

Give it a try, i had a very good feedback from my readers.

PS: This is will work if you have your action in good shape and it has to do with technique.