Richard Wagner’s Lohengrin is an opera that was completed in 1848 and is scored for a large orchestra, stage musicians and of course, singers. The clarinet section comprises four parts: 1st, 2nd, 3rd and bass clarinets. The 1st, 2nd and 3rd parts double on A and B-flat instruments. The bass clarinet part is written in A and B-flat.
Orchestras often (always?) perform this work with only three clarinettists: the third plays both parts: 3rd and bass, although these are published separately. I’ve observed players switching back and forth between the two paper scores and this can be pretty stressful if it’s your first season with the piece.
Here’s a PDF of an interleaved version of the 3rd and bass clarinet parts so that you can just turn the pages normally without switching between two parts. The areas to disregard along the way have been greyed out. In some cases this has lead to some pages being almost completely greyed out. It would be possible to cut and paste the part in the old-school way.
