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Re: Terminology of baseMoment, beats, groups

From: Hans Åberg
Subject: Re: Terminology of baseMoment, beats, groups
Date: Sat, 11 Nov 2017 15:07:44 +0100

> On 11 Nov 2017, at 12:52, Urs Liska <address@hidden> wrote:
> Am 11.11.2017 um 12:30 schrieb David Kastrup:
>> I find "grouping" without "beat" fine.  I could have been responsible
>> for the terminology in the code (pretty sure I wasn't, but it matches
>> the terminology I use quite better).
>> Now I have certainly not gotten an English music education, so can
>> someone who did chime in?
> I haven't either, but I can refer to Gould's terminology. While we all agree 
> that no single engraving book provides "the truth", it is surely a good idea 
> to match her terminology, if only to be able to communicate with 
> users/developers of other programs.
> She says: "Divisions of a beat are beamed together in all metres." and states 
> 2/4, 6/8, and 2/2 as metres of 2 beats. (p. 153, "Beaming according to the 
> metre")
> 3/2, and 9/16 are given as examples of metres of 3 beats.
> So it's clear that her terminology matches that of beatStructure, "beat" = 
> "beat" and "baseMoment" = "Division of a beat".
> The example I gave is also present in her examples (p. 155), other examples 
> of metres with beats of different lengths include 5/16 (2+3 or 3+2) and 7/8.
> So I think we can safely say the terminology of beatStructure is correct (or 
> at least acceptable).
> "Beat" also refers to what a conductor would do. the 3+3+2 from my example 
> would be given as three "beats" by the conductor. Maybe your perception of 
> "beat" as necessarily regular comes from the fact that in German we use 
> "beat" too, but usually referring to specific styles that are limited to 
> regular beats ...

"Beat" is synonymous with metric accent, but in practise, one also has metric 
subaccents. The notation indicates at which times the accents should occur, but 
not the actual length, and does not fully indicate their relative strength: In 
4/4, one knows that first beat should be strongest, but there are two common 
different interpretations for the others (see below).

It seemed easiest to me to define a formal (sub-)beat or metric (sub)-accent 
structure, which has a 1-1 correspondence with the beaming. Then the actual 
beaming used consists of a choice of such formal beat structures for different 
note patterns.

So the 4 above could have the other beats about the same in strength, or 
alternatively, a 2+2 pattern. There is also "in one" accent structure, whereby 
only the first beat is accented-whther to call the other unaccented time 
positions I leave up to you. This is normally not typeset, but one can choose 
it in Finale, I am told.

LilyPond fails in the subbeat structures: For example the common meter, 9/16, 9 
= (2+2)+(2+3), like in the Daichovo, is now typeset as 4+2+3, with a break in 
the beaming between the 2 and 3. It would be nice to be able having them beamed 
together at the top level, but broken on the second one.

As for the tuplets, one needs to have them in a group for the subbeaming to 
come out right. The default is the above in one pattern, except for certain 
multiples of 2 and 3—Hindemith describes those. So there is a problem in 
LilyPond relative the beaming if one is allowed to just write tuplet values 
instead of a full tuplet group.

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