Complex sentence: The sessions for "The Who By Numbers" began in April 1975 and lasted through early June, however the band did not begin the album tour until late in the year, which spanned some 70 concerts before concluding in the fall of 1976.
Split into simpler sentences: The sessions for "The Who By Numbers" began in April 1975 and lasted through early June. The album was released in October and the band began touring it, which spanned some 70 concerts before concluding in the fall of 1976.