(or @option{--format}) other output formats can be selected also, but
none of them work reliably.
-At the beginning of the output file, various global parameters are
-defined. Then the file @file{lilyponddefs.tex} is loaded to define
-the macros used in the code which follows. @file{lilyponddefs.tex}
-includes various other files, partially depending on the global
-parameters.
-
Now the music is output system by system (a `system' consists of all
staves belonging together). From @TeX{}'s point of view, a system is an
@code{\hbox} which contains a lowered @code{\vbox} so that it is centered