a few corrections/suggestions to the tutorial

[Pedro Kroger]

Hi,

I'd like to suggest a few corrections to "tutorial.itely" of lilypond 1.7.23

A couple of "\context Staff" missing around line 775 (on grace notes):

@lilypond[relative 1, verbatim,fragment]
\context Staff  \grace b16-( c4-)
  \grace { d16-( e } d4-)
@end lilypond

and in the section "Single staff polyphony" (line 1085), in the second
@lilypond code:

@lilypond[relative]
\context Staff  < { a4 g2 f4-~ f4 } \\
    { s4 g4 f2 f4 } >
@end lilypond

without them both examples are splitted in 2 staves. Speaking of
contexts, I feel that an introductory section about them
would be very useful. Any volunteers? :-))

When "\simultaneous" is introduced around line 643 the command
"\simultaneous" is used in the first example, but "<" e ">" is used
in the very next example. I'd suggest or to put the text of line 1075 
("The notation @code{< .. >} is a shorthand for @code{\simultaneous @") there,
 or replace "\simultaneous" for "<" and ">" in that example.

Cheers,

Pedro Kröger