Midi dynamics behaviour changed in latest git HEAD

[H. S. Teoh]

I've been using lilypond from git HEAD (mainly because lilypond in my
distro is too old, still stuck at 2.18, and I need features and fixes in
2.19), and recently I noticed that midi dynamics in my piano scores
aren't being rendered correctly anymore.  Looking into the commit log, I
saw this:

commit 980df8c5df55556b784d573f1c3d16bb9c8f3ab8
Author: Dan Eble <address@hidden>
Date:   Wed Jun 15 18:54:53 2016 -0400

    Issue 4947: Link notes to dynamics in Dynamic_performer rather than
    Staff_performer.  Dynamics in different voices are now independent.


It seems that this is the probable cause of the problem, because in my
piano scores I use a separate Dynamics context to put all dynamics,
something like this:

        rightHandPart = { c'1 ... }
        dynamicsPart = { s1\mf ... }
        leftHandPart = { c1 ... }

        % Note: this is for layout only
        \score {
                \new PianoStaff <<
                        \new Staff { \rightHandPart }
                        \new Dynamics { \dynamicsPart }
                        \new Staff { \leftHandPart }
                >>
                \layout {}
        }

        % This is what midi is actually generated from
        \score {
                <<
                        \new Staff << \rightHandPart \dynamicsPart >>
                        \new Staff << \leftHandPart \dynamicsPart >>
                >>
                \midi {}
        }

As you can see, \dynamicsPart is used for typesetting dynamics in the
layout score so that it will appear between the two staves, as is the
convention for piano notation. But for MIDI output I merge the dynamics
part with the parts for each hand. Prior to the above git commit, the
construct << \rightHandPart \dynamicsPart >> would cause dynamics to be
merged into \rightHandPart.  However, now it appears to be interpreted
as two separate voices with independent dynamics, so none of the
dynamics are applied to the actual notes anymore.

Is there some way to work around this?  How do I make lilypond merge the
dynamics from the Dynamics context into the LH/RH parts?

Thanks!


T

-- 
All men are mortal. Socrates is mortal. Therefore all men are Socrates.