⌂ Printing figured bass extender lines without a starting figure

In figured bass, the normal triads (<8 5 3> or simply <5> in LilyPond notation) are not printed at all. However, sometimes, the bass moves, while the upper voices in the chord should stay from the normal triad. The usual way for this is to print an extender line without an explicit starting figure. The simplest way to obtain this in LilyPond is to specify an underscore instead of the figure, which is interpreted as a space, so that only the extender line is shown. An alternative is to declare a bass figure as implicit, using the implicitBassFigures property of the Staff context. The most common setting would be \set Staff.implicitBassFigures = #'(5), which declares <5> an implicit figure and does not print the 5, but will print any extenders derived from it.