Extensions .sly and .fly deprecated?

[Heikki Johannes Junes]

I can see that lilypond-mode.el has still some relics of handling files
whose extension is .sly or .fly instead of .ly. I figured out that these
old extensions were used so that there may not be a \score-field.

I ended up to this problem when had an idea to put in work the compiling of
some region in a lilypond-code. Maybe it is difficult to make such
region-compiling facility and there is even no actual need for compiling
only part of a score (which may not contain a score-field).

Are this extensions still used in some form?

And, is there some command with which one can compile a region which does not
contain a score-field?

Or, should this Command-on-Region in Emacs be taken away, i.e., would
there be need for such facility?

Greetings,

  Heikki