Erbarme dich mein, o Herre Gott
is the most extended of all the sets, having six sections which fall into three pairs. In each of the first four verses the tune appears alternately in the soprano and the bass. The accompanying voices are derived from the tune and treated imitatively. The melody returns to the top part for variations 5 and 6, the latter being an extravagantly decorated version.
from notes by Stephen Westrop © 2003