In the manual 2.18
http://lilypond.org/doc/v2.18/Documentation/notation/guitar
I found the example for harmonic
\relative c' {
\clef "treble_8"
\override Staff.NoteHead.style = #'harmonic-mixed
d^\markup { \italic { \fontsize #-2 { "harm. 12" }}} 1
}
could not switch back to normal
BB writes:
> In the manual 2.18
> http://lilypond.org/doc/v2.18/Documentation/notation/guitar
> I found the example for harmonic
>
> \relative c' {
> \clef "treble_8"
> \override Staff.NoteHead.style = #'harmonic-mixed
> d^\markup { \italic { \fontsize #-2 {