This is a very common thing in music and I would say more the Norm than one might think. Historically often librettists where responsible for texts. For exampl

This is a very common thing in music and I would say more the Norm than one might think. Historically often librettists where responsible for texts. For example in opera there the librettist was as important as the composer and his texts might have been used in multiple operas. Among the most famous examples would be the European hymn Freude schöner Götterfunken. The text is by Schiller and the music by Beethoven.