\version "2.14.2"

\header {
  texidoc = "
When writing a figured bass, you can place the figures above or below
the bass notes, by defining the @code{BassFigureAlignmentPositioning
#'direction} property (exclusively in a @code{Staff} context). Choices
are @code{#UP} (or @code{#1}), @code{#CENTER} (or @code{#0}) and
@code{#DOWN} (or @code{#-1}).

This property can be changed as many times as you wish. Use
@code{\\once \\override} if you don't want the override to apply to the
whole score. 

"
  doctitle = "Adding a figured bass above or below the notes"
}
bass = {
  \clef bass
  g4 b, c d
  e d8 c d2
}
continuo = \figuremode {
  <_>4 <6>8
  \once \override Staff.BassFigureAlignmentPositioning #'direction = #CENTER
  <5/>8 <_>4
  \bassFigureStaffAlignmentUp
  < _+ >4 <6>
  \set Staff.useBassFigureExtenders = ##t
  \bassFigureStaffAlignmentDown
  <4>4. <4>8 <_+>4
}
\score {
  <<
    \new Staff = bassStaff \bass
    \context Staff = bassStaff \continuo
  >>
}