Generating music expressions from within \applyContext?

[H. S. Teoh]

Hi,

I have a Scheme function that returns a music expression. Unfortunately,
the expression returned depends on the properties of the context it's
evaluated in. I.e., based on the current setting of
Staff.dynamicAbsoluteVolumeFunction it will return a different number of
events in the music expression.

Is this possible?

The background of this is that I'm writing a Scheme function that
generates single-note crescendos by emitting a series of \set
Staff.midiExpression = ... events. Currently I've written a Scheme
function that's able to generate these events; however, it requires me
to specify numerical starting / ending values for midiExpression. I'd
like to be able to specify dynamics instead of numerical values, and
have the Scheme function automatically look up the numerical values
based on the current volume function defined for the Staff.

However, so far I haven't been able to figure out how to read the Staff
properties except using \applyContext with a lambda, and AFAICT it's not
possible to return a music expression from this lambda?

Or is there another (hopefully simpler?) way to achieve what I want?


--T