Buzzing on the leadpipe, (aka foghorn), is a great way to begin a warm up. Foghorn is usually the first that I do in my daily routine, and I have found with several of my peers that foghorn actually does help with tone production because it helps to find the center of the horn. Foghorn is also a great way to get the blood flowing. I think that buzzing is really only good for one aspect of playing: training the ear. You do NOT play like you buzz, so that's why I think foghorn is more beneficial in preparing for a day of playing. Not to say buzzing isn't, it's just my personal opinion. Like the post above says, go and google search the Bill Adams daily routine. He talks about buzzing on the leadpipe there as well if you don't think my information was very plausible lol. Good luck man!