extended trill flat or sharp macro

[Paul Scott]

The following code works for extended trills:

trstyle = {
   \override TextSpanner   #'style = #'trill
   \override TextSpanner   #'edge-height = #'(0 . 1)
}
trstart = \notes { %\override TextSpanner   #'font-family = #'music
   \trstyle
   \override TextSpanner   #'edge-text
    = #(cons (make-musicglyph-markup "scripts-trill")  "")
}

\notes{ \trstart f1~^\startTextSpan f1 \stopTextSpan }

This works for trills with accidentals:

trillNatural = \markup { \musicglyph #"scripts-trill"
                        \raise #0.8 { \natural } }
trillFlat = \markup { \musicglyph #"scripts-trill"
                        \raise #0.8 { \flat } }
trillSharp = \markup { \musicglyph #"scripts-trill"
                        \raise #0.8 { \sharp } }

Now how do I learn how make-musicglyph-markup works so I can combine the 
two as I have started to do here?:

trflatstart = \notes{
   \trstyle
   \override TextSpanner #'edge-text =
   #(cons (make-musicglyph-markup "
...

Thanks for any ideas,

Paul Scott