tocItem as \mark

[David Sumbler]

I want to have a table of contents with the titles of sections of a
piece and the relevant page numbers.

In pieces I have set previously, the title of each movement was placed
centrally over the first line of the score/part for that movement.  I
set the variable "piece" in the header for each movement, and defined
scoreTitleMarkup to get the result I wanted.

The piece I am currently working on is a single score, but with 6 songs
which follow each other more or less continuously.  I want the title of
each song to appear above the top line of the score at the start of
each song; in most cases this will probably not be at the start of a
line.

I thought that I could do this by inserting the title as a text mark,
e.g. \mark \markup { \fontsize #2 \bold "Title of song" }, with an
override to left-align the title.

This works as intended, but if I then put \tocItem before \mark
Lilypond complains that \tocItem has to be followed by markup; if I put
\tocItem after \mark Lilypond complains that \mark has to be followed
by markup.

Is there a way this can be made to work?  Or how else might I get the
desired result?

David