Defining a new markup command (e.g. \lower by a specified amount)

[Philip Thomas]

I am having great difficulty getting the hang of defining new markup commands.

The examples given in the Extending 
manual in section 2.2.3 "New markup command definition" are comprehensible to 
me in their own right, but they aren't 
exactly simple examples, and I have so far failed to adapt definitions found in 
the scm/define-markup-commands.scm file 
to make my own new commands.

The particular problem that I'm trying to get to grips with at the moment is 
this:

I 
want to use the \lower command at about 15 places in text in a \markup block 
(i.e. outside the \score block). The 
\lower command works just fine to get the spacing I want between sections of 
text (whereas both \override #'(baseline-
skip . xx) and \vspace #xx have proved quirky). The problem is that I don't at 
this stage know exactly how much I want 
to lower the text by (\lower #xx). When the overall layout of the score is 
settled, I would like to experiment with 
different values of N, without having to change each \lower command separately. 
The solution seemed to me to be to 
define a new markup command (e.g. \dropNextline) which specifies the amount to 
which the line should be lowered. Then 
my 15 entries could all read \dropNextLine { text text text }, and the 
experiment would only involve changing the value 
of xx in the define-markup-command code until the overall spacing is correct 
when judged by the eye. But I'm bu**ered 
if I can get it to work. Sorry if I'm ignorant of something I should have found 
in the documentation.

I guess I have 
two questions:

(1) How to define a suitable \dropNextLine command?

(2) Is there an explanation anywhere from which I 
can learn in a graded, structured, way how to define my own markup commands so 
I don't have to presume repeatedly upon 
the kindness of other users on the forum? Are there some examples which would 
lead me by the hand a bit more gently, 
starting from the commands scm/define-markup-commands.scm and working them up 
into a useable result?

By the way, I 
have found define-music-function code much easier to handle, although I readily 
admit to being rather a beginner.


Cheers, Philip