Opening chorus
Opening choral movement, for instance of a cantata.
What it means
The opening chorus is the opening choral movement of a multi-part vocal work, especially of the cantata. It stands at the beginning, presents the theme of the work, and is often the most extensive and elaborate movement of the whole. In the church cantata its text usually relates to the reading or to the chorale of the respective Sunday and thus gives the frame for everything that follows.
Musical use
For the layout of such movements there are different ways: a large-scale movement with an independent orchestral ritornello into which the choir is embedded; a chorale setting in which one voice carries the melody in long values while the others play around it; or a fugal movement. Common to them is that the opening chorus sets weight and fixes the key, the character, and often the thematic material of the work. It is as a rule followed by recitatives and arias that carry the thought further before a closing chorale sums up.
In Bach's cantatas and Passions the opening chorus is often the most extensive movement, with orchestral prelude and artful working out of a chorale or a Bible verse.
Performance practice
Plan your strength, for the opening chorus stands at the beginning but is often the most strenuous movement; too massive a start takes its toll later. Work out the layout: if there is a cantus firmus, it must stay audible; in fugal movements the entries must be clear. Settle tempo and articulation with the orchestra early, because ritornello and choral movement must fit together. Watch for intelligibility of the text in dense polyphony and settle the distribution of syllables in melismas.
Bear in mind that the opening chorus often presents the entire thematic material of the work: whoever works it up should know the following movements, because connections can be made clear. Check whether a chorale melody underlies it, and make it audible.
In rehearsal planning, state the duration of the movement, because it determines the division of the whole session.
Also check whether the instrumental parts agree with the choral movement in the same version.