Re: 3 part fugue

[Mark Polesky]

Hu Haipeng wrote:
> I'm learning counterpoint. The 3 part fugue below is on 2
> staves.  I used both << >> and new voice, but my teacher still
> said the result is not good. Why?

You need to organize your stem directions with the commands
\voiceOne, \voiceTwo, and \oneVoice.  Basically, \voiceOne puts
stems and slurs etc. up, and \voiceTwo puts them down.  \oneVoice
makes stems and everything else return to their normal behavior as
when the voice is alone on its own staff.

So, when two voices share one staff, set \voiceOne for the higher
one and \voiceTwo for the lower one.

When a voice is alone on a staff, use \oneVoice for that voice.
At the beginning of a measure where another voice enters the staff
that was previously holding only one voice, switch the voice that
was just alone to \voiceOne (if the new voice comes from below) or
to \voiceTwo (if the new voice comes from above).

For the voice that switches from one staff to another, switch from
\voiceTwo to \voiceOne (if the voice moves from the upper staff to
the lower staff) or from \voiceOne to \voiceTwo (if the voice
moves from the lower staff to the upper staff).  But don't switch
the voice-type at the beginning of the measure for the
staff-switching voice.  Instead, enter the new command just before
the first note in the new staff.

For the voice that was previously sharing a staff and then is left
alone by the departure of the staff-switching voice, set the new
alone voice to \oneVoice at the beginning of the measure after the
departure (if the departing voice switches in the middle of a
measure), or at the beginning of the measure containing the
departure (if the departing voice switches directly at the
beginning of the measure).

This will ensure that the stems will be oriented properly.

So in your case, at the very beginning of the score, voices "one"
and "two" will share the "rh" staff, so set \voiceOne for voice
"one", and set \voiceTwo for voice "two".  At the same time, voice
"three" is in the "lh" staff alone, so you should set \oneVoice
for voice "three".

Then, in the last beat of measure 12, voice "two" switches from
the "rh" staff to the "lh" staff.  Immediately before that note
(fis), enter \voiceOne for that voice.  Now at the beginning of
that measure (12) enter \voiceTwo for voice "three", since it will
now need downstems to accommodate its new neighbor from above.
Then at the beginning of measure 13, enter \oneVoice for voice
"one", since it has the "rh" staff to itself.

Hope this helps.
- Mark