The video touches on the dark final years of both Kirnberger and his patron Anna Amalia; the chorale fits that subject. The score is available both from IMSLP and from Auke Jongbloed (http://partitura.org/index.php/johann-philipp-kirnberger-herzlich-tut-mich-verlangen/ ). Auke has both the version published by J.C. Kühnau (in A Minor) and the C Minor version of various manuscript copies (see video).