[MEI-L] Beat in 6/8

[Craig Sapp]

Hi Benjamin,

The problem is the ambiguous/conflicting terminology in this sentence:

On 27 August 2015 at 01:19, Benjamin Wolff Bohl <bohl at edirom.de> wrote:

> meter.unit contains the number indicating the beat unit, that is, the
> bottom number of the meter signature.


The problem is that in compound meters such as 6/8
    https://en.wikipedia.org/wiki/Meter_(music)#Compound_meter
The "musical beat" is a dotted quarter note, while the MEI "beat unit" is
an eighth note.  Using the word "beat" in such a way is unfortunate as it
can conflict with the musical definition of a beat, and this will continue
to cause mis-interpretation of what a beat is.

The duration of a beat is necessary for music analysis, since the treatment
of dissonance and consonance is tied to the location of a note on or off of
the beat.  The musical beat is also needed to automatically beam notes.
Implicit interpretation of the musical beat can be done with 6/8 by
assigning it to be a dotted quarter note, but there are exceptions to this
definition which would require a way of assigning an explicit duration to
the musical beat.

For example, the middle slow movements in a piano sonata may be labeled as
6/8, with the beat actually assigned to the eighth note, in which case the
"musical beat" and the MEI "beat unit" are the same.

Another more common corner case would be time signatures such as 3/8.  Is
that a compound meter with one beat in a measure, or a simple meter with
three beats in the measure (a variant on a 3/4 meter also possible in slow
movements)?

And of course in modern music with irregular meters such as 5/8, the
musical beats in the measure may may have two beats as 3+2 eighth notes, or
2+3 or a mixture of both in different measures.

Compound meters resulted in a degeneration of mensural notation.  Since
modern rhythms are always "imperfect", to emulate a perfect mensuration
dots are added to the notes (which would usually be implicit the mensural
metric equivalent).  These are represented as compound meters in modern
notation (who knows why they did not invent "2/4." time signatures instead
of "6/8" for such cases).  The problem is that modern time signatures are
ambiguous, since 6/8 could be considered like C-dot, or it could be
considered as a non-compound meter with 6 beat at the eighth-note level.

I whine to Perry every once in a while about this, so we can wait for his
reply on how to disambiguate such cases...

-=+Craig
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