define custom drums

[Herman]

Hi,

I am working on customizing some drum notation. From the tutorial I got this

#(define mydrums '(
(bassdrum default #f -1)
(snare default #f 0)
(hihat cross #f 1)
(pedalhihat xcircle "stopped" 2)
(lowtom diamond #f 3)))

It works but I don't know what I am doing. Wat does #f means? or "stopped"?
Where can I read about this format?

next I have defined my own note in postscript like this

tomNoteHeads = \override NoteHead #'stencil = #circSlashStil

Where circSlashStil is the defined character in postscript code. I can call this
using \tomNoteHeads (this works!) but I would like to define it as above in
mydrums. However this doesn't work. How can I integrate my custom note into my
definition?