The basis of the concertos is a set of four sonnets, quite possibly written by Vivaldi himself. These sonnets appear in the printed edition and an explicit connection is made between specific lines of the poems and specific passages in the music. The evidence for Vivaldi as poet lies in the fact that each of the sonnets lends itself excellently to the form of his concertos: a fast movement, a slow movement and another fast movement to conclude.
The middle of each sonnet has material suitable for that slow middle movement: In the spring, the slow movement depicts a goatherd sleeping with his faithful dog at his side. In the summer, it’s a tired shepherd who can’t sleep because of his fear of lightning, thunder, flies, and hornets. In the autumn, the mild air puts everyone to sleep. And, finally, in winter, the slow movement represents quiet contented days by the hearth.
This is the Autumn sonnet:
The peasant celebrates with song and dance
The harvest safely gathered in.
The cup of Bacchus flows freely, and many
Find their relief in deep slumber.
II. Adagio molto
The singing and the dancing die away
As cooling breezes fan the pleasant air,
Inviting all to sleep
Without a care.
The hunters emerge at dawn,
Ready for the chase,
With horns and dogs and cries.
Their quarry flees while they give chase.
Terrified and wounded, the prey struggles on,
But, harried, dies.
I’ll refrain from commenting on the wisdom of hunting while hungover, but I will invite you to listen for the details in the concerto: