Tomorrow is the Winter Solstice, the day when there’s the shortest amount of daylight of the year – and a perfect time to reconsider the all but microscopic middle movement of Bach’s Brandenburg Concerto No. 3. On the printed score, it’s only one measure long, containing two chords that aren’t even in the same key as the movements on either side of it. And yet, it gives performers the freedom to improvise and embellish to their heart’s content.

The one measure ‘Adagio’ is a Phrygian half-cadence, which although a typical (if not quite resolved) way of ending a phrase, here is isolated into just the two chords. But many today choose to embellish it with flourishes – from any combination of the violins, violas, cellos, and harpsichord that are playing. It creates a natural break in tempo and energy from the spirited first and final movements, which is why drawing it out into a longer pause seems like a way to help balance the divisions. Sometimes a separate piece of music will be swapped in, as also might have happened in Bach’s day. Others, like in the Freiburg Baroque Orchestra performance below, use it simply as a place to catch one’s breath, ever so briefly.

The Adagio movement in this video from Voices of Music is from 5:36 to 5:45 (blink and you’ll miss it!)

In this performance, the Munich Bach Orchestra gets to rest while Karl Richter has an elaborate harpsichord cadenza from 6:09 until 7:13:

And in this one by the English Chamber Orchestra, they play an entirely different piece (with the same Phrygian half-cadence ending) from 5:38-8:10: