Prall in brackets? (mordents as well)

[Boris Dušek]

Hi,

typesetting prall works just fine, but what should I do if I want to
typeset the prall in brackets? I got inspired by the dynamics
documentation on forte in brackets[1], but that did not work:

a \markup{\bracket{\prall}}

It throws the following error:
error: syntax error, unexpected \markup
  bes
     \markup{\bracket{\prall}} a r a


Is there a way to do that in LilyPond? Thanks for any tips.

Regards,
Boris Dušek

[1]: 
http://lilypond.org/doc/v2.10/Documentation/user/lilypond/New-dynamic-marks#New-dynamic-marks