What do these warnings mean and why are they occurring?

[Patrick Karl]

I have a LilyPond file, Sonata_Op6No10_atb_TB_100.ly-preprocessed.ly, which 
emits the following log file when compiled:

> Pats-Mac-Pro:test_articulate pat$ lilypond $f
> GNU LilyPond 2.14.0
> Processing `Sonata_Op6No10_atb_TB_100.ly-preprocessed.ly'
> Parsing...
> Interpreting music... 
> Interpreting music... 
> Interpreting music... 
> Interpreting music... 
> Interpreting music... 
> Interpreting music... 
> warning: MIDI channel wrapped around
> warning: remapping modulo 16
> warning: MIDI channel wrapped around
> warning: remapping modulo 16
> warning: MIDI channel wrapped around
> warning: remapping modulo 16
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed.midi'...
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed-1.midi'...
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed-2.midi'...
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed-3.midi'...
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed-4.midi'...
> MIDI output to `Sonata_Op6No10_atb_TB_100.ly-preprocessed-5.midi'...
> success: Compilation successfully completed

This is Corelli's trio sonata Opus 6 No 10.  It has six movements, each of 
which is in their own score block in this file.  I use Peter Chubb's articulate 
facility in order to generate better midi files.

As I read the log file, the problem is with the sixth movement.  If I comment 
the first five score blocks out, the above warnings do not occur.  I have 
compared the two resulting midi files for the sixth movement and they are 
identical.  However, I have several dozen similar files, and I don't want to 
have to do that kind of investigation each time one of them gets recompiled.

>From what I noted in the previous paragraph, it would appear that there is 
>some initialization with respect to midi file generation that needs to be done 
>whenever a new score block is encountered.  Does anyone agree with this?

In general, what is the proper way to get more information about the various 
error messages and warnings that appear in the log file?  To my knowledge, 
there isn't any comprehensive documentation of these messages.  Or?

I was using a previous version of the articulate script under LilyPond 2.12.3.  
These warnings did not occur there.