multiple dynamics marks next to each other

[Claus Atzenbeck]

Hello all:

I need to engrave multiple dynamic marks next to each other, indicating 
different dynamics for various repeats. Something like this:

    xxx x xxx xx (some notes)
    p - mf - f - ff

Currently I'm using this snippet:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    f,
      _\markup{\italic
        \musicglyph #"p" " - "
        \musicglyph #"m" \musicglyph #"f" " - "
        \musicglyph #"f" " - "
        \musicglyph #"f" \musicglyph #"f"
      }
      ^\markup{\italic "(vamp as desired)"}
    f' f, f' f, f' f, f' |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It works, except that there is no glyph for ff (or mp or mf etc.). My 
solutions shows too much space between the f and f (for ff) or m and f 
(for mf).

How is this best be solved in LilyPond? \musicglyph #"mf" does not work 
as expected.

Thanks for any hint.

Best,
Claus