Has anyone any advice/reading/diagrams/pictures on how to use 4 Mallets?
Andy -
I'm not aware of anything on the Internet describing four-mallet techniques, but these two textbooks should help you out:
For the Stevens/Musser grip: "Method of Movement for Marimba" by Leigh Howard Stevens. Pictures and text descriptions "straight from the horse's mouth" regarding the mechanics of Leigh's grip; also contains much very good information - but not necessarily "grip-specific" - regarding the way one moves about the marimba in general.
For the Burton grip: "A Musical Approach to Four Mallet Technique for Vibraphone (vol. 1)" by Dave Samuels. Diagrams and text descriptions of the mechanics of the grip. Best concise print explanation I've seen regarding the Burton grip.
Both texts also include technical exercises; on this count, Leigh's book goes into much greater detail than the Samuels book.
Hope these help. Both should be available from Steve Weiss or LoneStar Percussion; maybe even from amazon.com.
JW
The Stevens book.