Adding a figured bass above or below the notes

When writing a figured bass, you can place the figures above or below the bass notes, by defining the BassFigureAlignmentPositioning.direction property (exclusively in a Staff context). Choices are #UP (or #1), #CENTER (or #0) and #DOWN (or #-1).

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

\version "2.24.0"

bass = {
  \clef bass
  g4 b, c d
  e d8 c d2
}

continuo = \figuremode {
  <_>4 <6>4 <5/>4
  \override Staff.BassFigureAlignmentPositioning.direction = #UP
  %\bassFigureStaffAlignmentUp
  < _+ >4 <6>
  \set Staff.useBassFigureExtenders = ##t
  \override Staff.BassFigureAlignmentPositioning.direction = #DOWN
  %\bassFigureStaffAlignmentDown
  <4>4. <4>8 <_+>4
}

\score {
  <<
    \new Staff = bassStaff \bass
    \context Staff = bassStaff \continuo
  >>
}