http://www.clevelandorchestra.com/recordingsBroadcasts/Szell.Collection.asp

Szell's final five seasons as music director, when
the Orchestra (in cooperation with Cleveland radio station WCLV)
began taping almost every concert for possible inclusion
in its national radio broadcast series.
All were taped in stereo and are from concerts at Severance Hall in Cleveland,
except for the Sibelius Seventh Symphony on Disc 5,
which was taped in mono for Finnish Radio from a performance in Helsinki
during the Orchestra's eleven-week tour to Europe and Russia in 1965.