Found this reference on one of those file-sharing networks:
Kraftwerk - K4 (1971)
Gondel Kino, Bremen, Germany
June 25, 1971
01. Kraftwerk - Heavy Metal Kids (07:54)
02. Kraftwerk - K1 (15:39)
03. Kraftwerk - K2 (Ruckzuck) (19:20)
04. Kraftwerk - K3 (15:19)
05. Kraftwerk - K4 (11:30)
Total playing time: 69:42
There isn't any extra information about this this either in the liner notes
or on the interweb thing - however, as you listen it becomes obvious that
this is indeed a recording of the rather short-lived lineup of Kraftwerk
that includes Michael Rother and Klaus Dinger in its ranks! That's right -
Neu! as part of Kraftwerk!!! Are you still reading? Why aren't you
downloading instead?!
It's basically a whole CD of extended "side-long" jams in the style of the
first Kraftwerk albums performed in front of a small but enthusiastic
audience and broadcast on Bremen Radio in 1971. The members of Neu! really
take a forward role here, with Rother's guitar driving things for most of
the time and sounding quite rocking, with glimpses of his future soaring
melodic sound in the extended jam passages. The guitar and drums are backed
up by synth and I believe organ bass, with notable exceptions of flute
taking the forefront on the great version of Ruckzack (from the first
Kraftwerk LP) and is it distorted electric violin on K4? Maybe just Rother
taking a violin bow to his guitar strings! Proto-Kraftwerk and proto-Neu!
It's exciting stuff, and on top of that the sound quality is excellent -