+Normally staves are stacked vertically. To make
+staves maintain a distance, their vertical size is padded. This is
+done with the property @code{minimumVerticalExtent}. It takes a pair
+of numbers, so if you want to make it smaller from its, then you could
+set
+@example
+ \property Staff.minimumVerticalExtent = #'(-4 . 4)
+@end example
+This sets the vertical size of the current staff to 4 staff-space on
+either side of the center staff line. The argument of
+@code{minimumVerticalExtent} is interpreted as an interval, where the
+center line is the 0, so the first number is generally negative. you
+could also make the staff larger at the bottom by setting it to
+@code{(-6 . 4)}. The default value is @code{(-6 . 6)}.
+
+Vertical aligment of staves is handled by the
+@internalsref{VerticalAlignment} grob, which lives at
+@internalsref{Score} level.
+
+The piano staffs are handled a little differently: to make cross-staff
+beaming work correctly, it necessary that the distance between staves
+is fixed. This is also done with a @internalsref{VerticalAlignment}
+grob, created in @internalsref{PianoStaff}, but a forced distance is
+set. This is done with the grob property #'forced-distance. If you
+want to override this, use a @code{\translator} block as follows:
+@example
+ \translator @{
+ \PianoStaffContext
+ VerticalAlignment \override #'forced-distance = #9
+ @}
+@end example
+This would bring the staffs together at a distance of 9 staff spaces,
+and again this is measured from the center line of each staff.
+
+
+
+@node Horizontal spacing
+@subsection Horizontal Spacing
+
+The spacing engine translates differences in durations into
+stretchable distances (``springs'') of differing lengths. Longer
+durations get more space, shorter durations get less. The basis for
+assigning spaces to durations, is that the shortest durations get a
+fixed amount of space, and the longer durations get more: doubling a
+duration adds a fixed amount of space to the note.
+
+For example, the following piece contains lots of half, quarter and
+8th notes, the eighth note is followed by 1 note head width. The The
+quarter note is followed by 2 NHW, the half by 3 NHW, etc.
+@lilypond[fragment, verbatim, relative=1]
+ c2 c4. c8 c4. c8 c4. c8 c8 c8 c4 c4 c4
+@end lilypond
+
+These two amounts of space are @code{shortest-duration-space}
+@code{spacing-increment}, grob properties of
+@internalsref{SpacingSpanner}. Normally @code{spacing-increment} is
+set to 1.2, which is the width of a note head, and
+@code{shortest-duration-space} is set to 2.0, meaning that the
+shortest note gets 2 noteheads of space. For normal notes, this space
+is always counted from the left edge of the symbol, so the short notes
+in a score is generally followed by one note head width of space.
+
+If one would follow the above procedure exactly, then adding a single
+32th note to a score that uses 8th and 16th notes, would widen up the
+entire score a lot. The shortest note is no longer a 16th, but a 64th,
+thus adding 2 noteheads of space to every note. To prevent this, the
+shortest duration for spacing is not the shortest note in the score,
+but the most commonly found shortest note. Notes that are even
+shorter this are followed by a space that is proportonial to their
+duration relative to the common shortest note. So if we were to add
+only a few 16th notes to the example above, they would be followed by
+half a NHW:
+
+@lilypond[fragment, verbatim, relative=1]
+ c2 c4. c8 c4. [c16 c] c4. c8 c8 c8 c4 c4 c4
+@end lilypond
+
+The most common shortest duration is determined as follows: in every
+measure, the shortest duration is determined. The most common short
+duration, is taken as the basis for the spacing, with the stipulation
+that this shortest duration should always be equal to or shorter than
+1/8th note. The shortest duration is printed when you run lilypond
+with @code{--verbose}. These durations may also be customized. If you
+set the @code{common-shortest-duration} in
+@internalsref{SpacingSpanner}, then this sets the base duration for
+spacing. The maximum duration for this base (normally 1/8th), is set
+through @code{base-shortest-duration}.
+
+@cindex @code{common-shortest-duration}
+@cindex @code{base-shortest-duration}
+@cindex @code{stem-spacing-correction}
+@cindex @code{spacing}
+
+In the introduction it was explained that stem directions influence
+spacing. This is controlled with @code{stem-spacing-correction} in
+@internalsref{NoteSpacing}. The @code{StaffSpacing} grob contains the
+same property for controlling the stem/barline spacing. In the
+following example shows these corrections, once with default settings,
+and once with exaggerated corrections.
+
+@lilypond
+ \score { \notes {
+ c'4 e''4 e'4 b'4 |
+ b'4 e''4 b'4 e''4|
+ \property Staff.NoteSpacing \override #'stem-spacing-correction
+ = #1.5
+ \property Staff.StaffSpacing \override #'stem-spacing-correction
+ = #1.5
+ c'4 e''4 e'4 b'4 |
+ b'4 e''4 b'4 e''4|
+ }
+ \paper { linewidth = -1. } }
+@end lilypond