Re: Partial

[Joseph Austin]

Date: Fri, 17 Mar 2017 21:48:50 +0100
From: David Kastrup <address@hidden>
To: Joseph Austin <address@hidden>
Cc: address@hidden
Subject: Re: Partial
Message-ID: <address@hidden>
Content-Type: text/plain

Joseph Austin <address@hidden> writes:

I've been experimenting with \partial, the command for scoring
anacrusis, and discovered some apparently undocumented features.

First of all, although I did not see it in the documentation,
the form \partial DUR*NUM, such as \partial 8*5, seems to work, where
NUM is an integer multiplying DUR.

Multipliers are an optional part of _all_ durations, so DUR*NUM would be
redundant.

This seems to be sufficient to accommodate any arbitrary anacrusis,
(except possibly partial tuplets, but I'm not sure such rhythms occur
in practice).

Multipliers can be fractions.  \partial 4*3/7 will also work.

Also, durations specified with dots also work, e.g  \partial 4..

Should these options be added to the documentation?
(Or perhaps it's already there but I missed it.)

All those can be part of _any_ duration.  Nothing specific to \partial .

--
David Kastrup
========================================

Notation Reference 1.2.1 

Scaling durations

The duration of single notes, rests or chords may be multiplied by a fraction N/M by appending *N/M (or *N if M is 1) to the duration. This will not affect the appearance of the notes or rests produced, but the altered duration will be used in calculating the position within the measure and setting the duration in the MIDI output. Multiplying factors may be combined like *L*M/N. Factors are part of the duration:

From reading this, given that it does say the altered duration will be used in calculating the position within the measure, perhaps I should have concluded that it would apply to \partial and have the desired effect, but I was more focused on This will not affect the appearance of the notes or rests produced  In any case, I tested it and it does work.

But thinking about it, I'm wondering why one would want to notate a different duration than is actually played,

for instance, applying David's later example:  

( \partial 8*2/3*2 (8*2/3 being _one_ eighth note triplet).

as follows:

First, use the formula as a duration multiplier:

c8*2/3*2 d e f g a b c d e f g a

In this case, each note is notated as 1 eighth, but counted as 4/3 of an eighth-note, giving 6 eighth-notes per 4/4 measure.

| c8 d8 e8 f8 g8 a8 | b8 c8 d8 e8 f8 g8 | a

This is consistent with the description of Scaling Duration in the Notation Reference.

Now using the same multiplier as a partial for a scale in triplet eighth-notes:

 

\partial 8*2/3*2  \tuplet 3/2 {c8 d  e f g  a b c  d e f  g a b } c

It is notated as:  \tuplet 3/2 {c8  d8  |  e8 f8 g8   a8 b8 c8   d8 e8 f8   g8 a8 b8 } |  c8 

That is, an anacrusis of 2 triplet eighths..

This is both the nominal time and the allocated time (4/3 of an eighth).

Let me just say, for my purposes, I would like \partial to work the way it works now,

that is,  \partial 8*5  means a partial measure of five eighth notes,

both notated as such and counted as such.  

Without such an interpretation, I suspect there are amounts of anacrusis that could not be expressed,

such as five eighth notes.

However, I'm not sure the documentation is consistent with that interpretation.

I'm relatively new to Lilypond at this level of detail.  

All I can say is that the allowed forms and interpretation of \partial isn't so clear to me from the existing documentation.