Enter correctly flat and sharp notes

[Tommaso Gordini]

Hello to all,

here's a minimal code:

%%%%%%%%%%%%%%%%%%

\version "2.16.2"

\relative c {

\clef "bass"

\key c \major

\cadenzaOn

c,2

^\markup { \tiny { Serie armonica del fa (+: crescente; -: calante) } }

^\markup {\small { Corno in Fa } }

c' \clef "treble" g' c e g \stemUp bes4-- \stemDown c2 d e f4-+ g2 a4-- bes-+ b2 c

\cadenzaOff \bar "||"

}

\layout {

\context {

\Staff \remove "Time_signature_engraver"

}

}

%%%%%%%%%%%%%%%%%%

The quarter notes marked with '-' are flat, quarter notes marked with '' are sharp. What is the correct way to indicate it? I tried to draw the arrows, but I could not do it.

Ciao

Tommaso