South London called Broadway Sound. Early on the morning of August 12th 1982 the band, comprising of Colin Swan, Geno Buckmaster, Brian Grover and their trusty roadie ‘Robbo’ assembled at the tiny studio to begin recording as many of their songs as they could get down on tape for the tiny budget they had scraped together. As most of the songs were already well rehearsed thanks to the band’s busy live schedule, the recording of the first nine songs on this disc were finished by mid afternoon without any problems.
I just would like to know why the writer did not use past perfect .We can reasonably think that the action was completed and there is a link of causality.It is because the songs had been well rehearsed that the recording did not last long. It is obvious.
I think that is because both actions were too close. One happened just after the other within a little time and as the causality is obvious: no need for past perfect.
Or may be it is the expression "most of the songs" which implies that some of them needed to be rehearsed a little more so the action was not completed (in fact after thinking of it I think this is the reason for past simple)
Source: THE BROADWAY RECORDING SESSIONS A PIECE OF MOD HISTORY