I've always been curious about that as well. Those reductions are very handy. I can read three separate staff lines easily, but four is a constant struggle when we're rehearsing something.

Also, dynamic markings would be awesome! I'm more than happy to use someone else's dynamics. If an editor is competent enough to make a useful arrangement, I figure his/her dynamics are no doubt much better than I could come up with on the fly. : )

P.S. Many, many thanks to the CPDL editors for their editions and for their generosity in sharing them with the public. I don't know what I'd do without them, and I have so much fun browsing through all the music in my spare time.

It's like cocaine.

What is, KLS, the Jernberg, or the reliance upon the organ? ;-)

Idk about others but when I edit all those 3 voice pieces I've been posting and compile them together into one collection I'm definitely including reductions. For rehearsal purposes, for performance purposes, to be able to play through and choose if they're workable. Heck, for political purposes and for health reasons too. Whatever purposes apply. I just think its practical.

It's also interesting to see the same music scored different ways. Especially if conducting, I like the different perspectives offered by seeing the music on 1/2 staves compared with 3-8. Both highlight different aspects of what's going on.

Note: This is rather long, since I started right after Melofluent first posted in this thread, but with my different roles as editor, composer, conductor, singer, and administrator at CPDL, I have what probably has to be regarded as a multifaceted perspective:

Good question, Melo. I don't know if there is any general "ethos" about score preparation for (a cappella) polyphony, with regard to the inclusion of a keyboard reduction of the vocal score. I've prepared scores with keyboard reductions and without, sometimes for the same work. There are several factors involved, and these factors are dependent upon the perspective whether one is the creator of the score or the musician performing the work from the score or the musical director (or rehearsal acccompanist) trying to prepare a performance: utility for performance preparation, "qualitease" (think "quality" + "ease") of creating a keyboard reduction, "ecolonomy" (think "ecology" + "economy"), and even aesthetics. Let's take them up on reverse order.

Aesthetics: This issue mostly likely is appreciated by the ones singing a polyphonic work and by those (historians and musicologists, among others) who study polyphonic works. And there is simply the overall appearance of the score, which, for a score with rehearsal accompaniment, may well be subject to cramped spacing between staves and systems, too small staff height and text underlay font size, etc. – as opposed to an open, uncluttered layout that is easy to read.

Ecology & Economy: Generally, providing a rehearsal accompaniment will lengthen the vertical span of a score, thereby requiring an increase in the number of pages. For example, a 3-part score with rehearsal accompaniment (and with no extra compression of things such as spacing between staves, staff height,underlay font size) will require about 60% more vertical space – and if the score without rehearsal accompaniment fits 3 systems per page, the one with rehearsal will accommodate only 2 systems per page, resulting in about half again as many pages for the score as the one without accompaniment. This represents an additional hit on the paper consumed and money spent. It is most noticeable when a work that normally requires one 2-sided sheet of paper suddenly, thanks to the added keyboard reduction, requires two sheets of paper, even if only 3 of the 4 sides require printing.

Quality & Ease of creating: There are keyboard reductions and there are rehearsal accompaniments&bsp;– not quite the same, perhaps, but used more or less interchangeably elsewhere. Providing either of these for a 3-part work is relatively simple, and it is not too much more difficult for a 4-part work, although voice crossings and other considerations do require some thought and attention. For 5- and 6-part works, the ease of creating a viable rehearsal accompaniment (because of difficult choices, such a keyboard part could hardly be called a keyboard reduction). And for more parts, it is even worse, if often not almost impossible.

Utility for performance preparation: There is no doubt that some choral groups do indeed require rather extensive use of a keyboard for the preparation of a work for performance, whether by sheer force of tradition or by somewhat limited experience with singing a cappella. There is a downside to reliance on rehearsal accompaniment, in that all too often a group becomes overly dependent on the keyboard and fails to achieve a truly cohesive a cappella performance both because of insecurity of the singers in their individual parts but also because of poor intonation issues which equal temperament of the keyboard used for preparation reinforces negatively. Preparation of a cappella music should rely as little as possible on a keyboard during rehearsals.
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I have been blessed in the past by working with at least two groups, each of which had such a (rehearsal) accompanist that keyboard reductions were unnecessary (and, since we were singing from early music sources, were not available) but were skillfully provided by sight, on the fly, for as many as 8 parts in rehearsal. Also, with the early music ensemble with which I sang for a dozen years, keyboard for rehearsal was almost never used; moreover, when a keyboard was used, it was a harpsichord or positive organ tuned (if I recall correctly) in quarter-comma temperament.

As an editor/engraver of (mostly early) choral music and as a choral composer, conductor and singer, I've had to deal with issues often enough. I've been asked if I could prepare a rehearsal accompaniment for an upcoming performance of my 6-part "Ave verum corpus" – and I can assure you, this is not an easy task.

As another example, I published "This Advent Moon" (SATB divisi) with a rehearsal accompaniment, knowing that the groups singing it at the time would benefit from having it available; however, the result has two rather cramped systems per page, and I have never been aesthetically pleased with the result. A (not yet published) version without the rehearsal accompaniment still has two systems per page, but has an open, easy to read, uncrowded format that is much better. If I were to achieve such an open look for a version with rehearsal accompaniment, it would only allow one system per page, effectively doubling the number of pages from 8 to 15 (there is only one system on the first page even without accompaniment), and thereby doubling the number of sheets of paper from 4 to 8. And my SATB "Ave Maria" (which has no divis and is acceptable enough at 3 systems per page) requires 4 pages (two sheets of paper with 2-sided printing) without a rehearsal accompaniment, but it would go to 5 or 6 pages (three sheets of paper with 2-sided printing) if I were to publish it with a rehearsal accompaniment. My "Veni, Veni Emmanuel" setting is 8 pages (3 systems per page) without keyboard reduction, and 12 pages (2 systems per page) with keyboard reduction. When providing 40-60 scores, the added expense of providing everyone with a keyboard reduction edition is considerable.

A few other examples (not my own works, just my own editions): Josquin "Ave Maria ... Virgo Serena" (SATB) at 3 systems per page & no rehearsal accompaniment runs to 8 pages, and it would be 11 pages long with accompaniment; Mouton "Ave Maria ... Virgo Serena" (SATTB) at 2 systems per page & no rehearsal accompaniment runs 16 pages, and it would be 31-32 pages with accompaniment unless severe compression were employed to keep it at 2 systems per page (not at all advisable); Palestrina "O Magnum Mysteriu" (SSAATB) at 2 systems per page & no rehearsal accompaniment runs to a dozen pages, but it would be a full 24 pages long with accompaniment.

Enclosed is the unpublished "This Advent Moon" score with no keyboard reduction (it was never fully tweaked for publication). You can compare it with the published version at CPDL or somewhere here at the forums.

Of course, we could start publishing in part-book format. (Get your sackbuts ready!)

Close! I've sung from part-books before, and I played bass sackbut! And of course, I've prepared scores of early choral works from part-books, including several with sometimes cryptic instructions, usually for additional voices in some kind of canon with one or more of the parts.

As an aside, my own 3-part "Gustate et videte" (and "O taste and see") can e sung from a single part (which I included with the score).

Thank you, Charles, for the great explanation @ keyboard reductions. I had the dim idea that most music writing programs like Sibelius automatically generated keyboard them, and I didn't realize how much work it could be for the composer/editor, though I can easily understand how complicated it could get writing one that is more than 3 or 4 parts, and it makes perfect sense that aesthetically and economically speaking, it's far better not to have them in many polyphonic works.

The main reason I like them is so I can play them on the piano here at home to familiarize my family with a new piece a week or so before we begin rehearsing it together. However, since most of the pieces we sing now don't have a reduction, I have become more adept at sight-reading 4 and 5 part pieces which is no doubt a good thing. It does get easier the more one does it.

Thanks very much for the advice @ rehearsing acapella. When we first began singing polyphony several years ago, we relied a lot on the keyboard, and our vocal coach still insists on it the first few times we run through something, esp. for the sake of our tenor who always struggles a bit with his part, but I hate having the piano now during practice so you have actually beautifully confirmed my own instincts. It is such an interference and sounds so rude, harsh and jangly.

It is remarkable how one's musical perceptions change over time.

Anything up to four parts is quite simple to reduce so I almost always make reductions. Here is the simple method (for Sib users anyway). SATB for example, you select the Alto and Bass parts and hit Option - 2 which turns them into "second" voice parts.

Create a piano part. Then highlight the S part, and then clicking the option key click the first measure of the treble staff and it copies the part into the piano part. Do the same for Alto and copy into the treble staff. Then repeat the same for T and B in the Bass cleff of piano. Then, select the entire piano staff and filter out the lyrics and hit delete. Do the same for dynamics. I don't want any dynamics in a staff that is for rehearsal only.

Done. Takes about 1 minute.

Is there a philosophical reason...

A lot depends on who the editor imagines will be the user. In a large amateur group without good section leaders an accompanist can be extremely useful, and if one has scorewriting software it can be worth the trouble to make your own edition, especially if there's usable code on cpdl.

There are choruses with unpaid conductors and paid non-scorereading rehearsal accompanists out there, I know, but many of us are comfortable rehearsing a cappella work a cappella. As Chuck points out a rehearsal part can clutter the page, and can be the difference between two 6 or 8 staff systems per page and one. I would only add to his observations that page turns are going to be an issue for players and that some prefer reading from a well laid out score anyway.

Ryan, those are breath marks - singers tend to use that kind of marking because the 'comma' breath-mark instrumentalists use can sometimes end up looking like a, well, like a comma.

^This^
Brilliant post.
One of my choral mentors offered these little bon mots:
f = free (not loud, not full even.)
p = powerful (not soft, but condensed intensity)
Parenthetical remarks mine.

I also should mention that I use a small staff when doing reductions which again sends the message that 'this is not for performance'. It also saves room on the page as a full size grand staff is not necessary for rehearsal only reductions. Here is an example.

This is why we were required to read from open score at the keyboard in school. I have no qualms about judicious accompaniment of the voice parts. And there are times when it helps to have a written accompaniment. I remember feeling vindicated when I learned that there is extant a keyboard part for "Dum complerentur" in PALESTRINA's own hand. Perhap's even he occasionally needed a little "assurance".

Bring back the serpent!

I LOVE the Fontgambault recordings and the exquisite accompaniments. I often watch this video from 2:20 to 2:40 to observe the chantmaster conducting the schola. So many lessons to learn from that little sequence.

https://www.youtube.com/watch?v=pnKbPj7EhCg

Open score reading is still something I do not consider myself skilled at - partly because I've spent much more time conducting than accompanying. So I personally appreciate a reduction. That said, even with amateur choirs, I think the less piano the better in rehearsal. Even beyond the issue that the piano is ALWAYS out of tune (and even if it is not equal temperament - my rehearsal piano is Bach/Lehman, so it has some pure 5ths and good 3rds), singers always follow the piano rather than learning to lead with their voices. The percussive nature of the piano provides rhythmic leadership, that is suddenly missing when they try to go a cappella.
I try to use the piano as little as possible, and when I do use it, it is just to reinforce a voice part that is weak that day (say, only two sopranos showed up and they aren't strong readers). In those cases, it's easy to just read a voice or two off the open score. All of which to say, I think we're better off without reductions as they make it too easy to fall back on a crutch that is unhelpful in the long run.

As a little postscript to this discussion, thanks to Melo's recommendation, I ordered copies of Paul Jernberg's Salve Regina and received them in the mail today.

I'm very happy with the well laid out and clear presentation of the score. It's a very doable SATB with a few optional voices embellishing some phrases. The sumptuous harmonies and a very satisfying blend of western, eastern, modern and renaissance remind me very much of the contemporary Polish composer Pawel Bebenek's music.

https://www.youtube.com/watch?v=nL0B821MJl4