To use a normal font within a title, you must define it manually
#(def-markup-command (normal-font layout props arg) (markup?) "Switch to normal text font" (interpret-markup layout (cons '((font-series . 'medium) (font-shape . 'upright)) props) arg)) \header{ title = \markup{ ABCD \normal-font ABCD } }
This page is for LilyPond-2.6.3 (stable-branch).