From the recording Explorations

Schubert wrote the Shepherd on the Rock as a song for the unusual
combination of soprano, clarinet, and piano. This lovely arrangement by John Gibson replaces the soprano with cello.

The story of Shepherd on the Rock is that of a young man pining for his love far away. It begins with a description of the way his voice returns to him in an echo when he calls down the valley. The middle section is very melancholy, speaking of how joy has died in him. But, ultimately, youthful optimism wins out, as he looks forward to the coming of Spring.

Even without the words, you can clearly hear this progression of
feelings in the music - first lovely and at times declamatory, with the cello and clarinet trading lines to represent the echo, then melancholy, and finally exuberant and energetic.

Publisher: J.B. Linear