Ledger Lines in Key Signature?

[Frank Z.]

Dear Lilypond-Community,

I'd like to have a key signature with a flat on B3 (one octave lower
than usual). This can be achieved easily. But I would like to have a
ledger line for this key signature accidental. Is this possible?


\version "2.18.2"

\relative c' {

  \override Staff.KeySignature.flat-positions = #'(-1)

  \time 3/4
  \key d \minor

  d2.
}


The only way I know how to this, is rather creepy. Attatch a line to the
first note and change its offset so that it appears as a ledger line.
There must be a better solution.


\version "2.18.2"

\relative c' {

  \override Staff.KeySignature.flat-positions = #'(-1)

  \time 3/4
  \key d \minor

  \once \override TextScript.extra-offset = #'( -6 . 0.7)
  d2._\markup { \override #'(thickness . 2) \draw-line #'(1.5 . 0)}
}


Thanks alot for any help!

Best

Frank