Titling markup

[Thomas Scharkowski]

Hello list,

it seems to be an easy question, but I could not find a solution:
How can I change the formatting of "title" or "subtitle" to "normal" 
instead of "bold", without editing "titling.scm"?
I know how to change e.g. "dedication" to "bold" via \markup, but I 
could not find a reference for the other way around in
"7.4.3 Overview of text markup commands".
What is the opposite of "bold"?

Thank you,
Thomas

Lilypond 2.4.2
Cygwin