Re: voiceOne and oneVoice

[Lukas-Fabian Moser]

Hi Kira,

Am 30.09.21 um 00:32 schrieb Kira Garvie:
> I realize this is a pretty basic question... but what is the 
> difference between voiceOne and oneVoice? I am writing a multivoice 
> keyboard-style hymn (as opposed to SATB chorale style) and the 
> directions say to switch between oneVoice and voiceOne as needed for 
> stem direction...
> "(d) Add voiceOne and oneVoice tags throughout to indicate stem 
> direction. If
> there is no separately stemmed second part at the first note, oneVoice 
> is assumed."
> Do I need to give an example?

\voiceOne sets the layout for the current voice as if it is the first of 
several simultaneous voices.
\oneVoice sets the layout for the current voice as if it is an only voice.

If you do in-staff polyphony via

<<

{ \upperMusic } \\ { \lowerMusic }

>>

then the \\ makes LilyPond silently add a \voiceOne to \upperMusic and a 
\voiceTwo to \lowerMusic, making sure that \upperMusic has upward stems, 
articulations etc., and \lowerMusic has everything downwards.

Sometimes it is useful to switch back to "normal" one-voice layout even 
in a polyphonic enivoronment; that can be done using \oneVoice.

A typical application is

\once\oneVoice r8

for a single rest that should be centered mid-staff (often, the other 
voice then has a simultaneous skip: s8). But this construction is not 
needed that often anymore because now there is the Merge_rests_engraver 
that is able to collect simultaneous rests in polyphonic situations and 
merge them to a single ("\oneVoice", so to speak) rest.

As a rule, in writing polyphonic music, it's often useful to use 
\voiceOne, \voiceTwo etc. and \oneVoice, and there a comparatively few 
good situations to use an explicit \stemUp or \stemDown.

Is this clear enough without compilable examples?

Lukas