### 2.2.2 Multiple staves

LilyPond input files are constructed out of music expressions, as we saw in Music expressions explained. If the score begins with simultaneous music expressions, LilyPond creates multiples staves. However, it is easier to see what happens if we create each staff explicitly.

To print more than one staff, each piece of music that makes up a staff is marked by adding `\new Staff` before it. These `Staff` elements are then combined in parallel with `<<` and `>>`:

>     \relative c'' {
>       <<
>         \new Staff { \clef "treble" c4 }
>         \new Staff { \clef "bass" c,,4 }
>       >>
>     }

The command `\new` introduces a ‘notation context.’ A notation context is an environment in which musical events (like notes or `\clef` commands) are interpreted. For simple pieces, such notation contexts are created automatically. For more complex pieces, it is best to mark contexts explicitly.

There are several types of contexts. `Score`, `Staff`, and `Voice` handle melodic notation, while `Lyrics` sets lyric texts and `ChordNames` prints chord names.

In terms of syntax, prepending `\new` to a music expression creates a bigger music expression. In this way it resembles the minus sign in mathematics. The formula (4+5) is an expression, so -(4+5) is a bigger expression.

Time signatures entered in one staff affect all other staves by default. On the other hand, the key signature of one staff does not affect other staves. This different default behavior is because scores with transposing instruments are more common than polyrhythmic scores.

>     \relative c'' {
>       <<
>         \new Staff { \clef "treble" \key d \major \time 3/4 c4 }
>         \new Staff { \clef "bass" c,,4 }
>       >>
>     }

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#### LilyPond — Learning Manual v2.18.2 (稳定分支).