Types of Score Layouts
The “Score” I refer to in the title of this section means a choral score that is written on multiple staves. This may refer to choral parts written in typical pianistic fashion, with one treble staff and one bass staff that each contain multiple voice parts; or it may refer to multiple staves that contain one vocal part each.
The first example shows a score that positions four vocal lines onto a grand staff. This is the same layout as you will typically see in a hymnal.
The second example, also cited in the Basic Registration tab, demonstrates how the vocal parts may be positioned as in the example above, but with an instrumental accompaniment placed below the choral parts. As mentioned in Preparing for Rehearsal, the accompanist should be prepared to play the accompaniment by itself, all four voice parts together, any combination of two or three voice parts, or some combination of the choral parts along with the accompaniment.
A third type of score will position one voice part per staff in an open-score format, and add a keyboard reduction below the choral parts. This is common in modern publications and is probably in response to many accompanist’s inability to read open-score music. Try not to rely entirely on keyboard reductions, however, because they can diminish your skill not only at reading four voice parts, but two or three parts at a time. The ability to accurately sight-read one, two, or three parts at a time, whether in open score or in a reduction, is an essential skill for a rehearsal accompanist.
The last example shows an open-score format without a keyboard reduction. One sees this type of layout mostly in Renaissance music and in scores that are available for free (legally!) on websites such as CPDL and IMSLP. In this case, it is important not only to be able to understand the score as a whole, but to identify melodic entrances.
The degree to which you are expected to play choral parts will largely be determined by the conductor, but you should at least be able to comprehend the layouts above and play accurately in various combinations that are required and/or helpful.
How to Practice
Reading multiple choral staves is largely an extension of what we have already learned by this point in our keyboard skills, assuming we can already play the piano and organ. When we learn to play the piano or most other instruments, we start with notes on one staff. Eventually we learn how to read two staff lines on the piano: one for the treble and one for the bass. When we start to play the organ, we learn how to read an additional bass line. When we encounter our first organ trio, we learn how to navigate two trebles lines and one bass line. Learning how to read choral staves relies on a skill we have already developed: the ability to efficiently ready multiple staff lines at once. The biggest difference that we will encounter in most choral repertoire is that of the Tenor part, which is written with a treble clef but played one octave below the written note.
The suggestions mentioned in Tips for Practicing apply here, particularly the idea of varying the number of parts. When learning to play an open SATB (Soprano, Alto, Tenor, Bass) score, begin by playing all the combinations of two voices at a time: SA, ST, SB, AT, AB, and TB. Next, play all combinations of three voices at a time: SAT, SAB, STB, and ATB. Finally, play all four voices simultaneously.
Lastly, practice from scores that do not include a score reduction. That defeats the purpose.
Resources for further study
Beck-Slinn, E. 100 Graded Exercises in Vocal Score Reading. London: A. Weekes and Co., 1906.
Lang, C.S. Score Reading Exercises in 4 and 4 Parts: Book 1. Bury St. Edmunds, UK: Novello, 1949.
Morris, R.O. and Howard Ferguson. Preparatory Exercises in Score Reading. Oxford: Oxford University Press, 1931.