It sounds like XeLaTex does not have limit to at most 16 alphabets. However when I declared some alphabets and included many fonts(I indeed included fontspec), the message "Too many math alphabets..." occurred as usual.
Haven't I use the correct command?
Update
Edited title
My question:How to use abundant math font features in one article in XeLaTeX?
\famcan access them, but not any other primitive). – خالد حسني Feb 24 '13 at 23:50