Hi Stanislav,
By now you are probably overwhelmed with the number of responses to your query. I make extensive use of custom shape flags in my setting of New Complexity School music. Here’s what I do, which is to adjust the flag stencil, the code that draws the flag shape. The exisiting straight-flag function allows you to specify thickness, spacing, angle, and so on. If you use very thick flags you need to increase the spacing, and probably also the stem length of the notes to accommodate them. This seems to be a different approach to what the others are suggesting. There are many ways to do things in lilypond, since it is so powerful and flexible.
As to Musescore, I have never had success importing anything remotely sophisticated into lilypond. I would venture to suggest that if you are going to target lilypond as an end point in any case, that you would be well served by taking the time to learn lilypond, and enter your scores directly. It’s not hard, and as you have noticed, everybody will help you here.
If this technique proves to advanced, I am happy to look at sample of your desired output and adapt it to what you require, it that’s of any help.
Andrew
== snip
\version "2.19.42"
#(define thick-straight-flag
(lambda (grob)
((straight-flag 1.2 2 -45 1.2 45 1.4) grob)))
treble = {
\clef treble
\time 1/4
\autoBeamOff
c''8 c''16 \stemUp c''16
}
bass = {
\clef bass
\time 1/4
r32 c32
\stemDown
c8
}
\score {
\new PianoStaff
<<
\new Staff = "treble" { \treble }
\new Staff = "bass" { \bass }
>>
\layout {
\context {
\Score
\override Stem.length = #14
\override Flag.stencil = #thick-straight-flag
}
}
}
== snip