Stormtrooper, a little known and struggling band from London, had formed and disbanded in a space of 10 months in 1975, two years before punk rock had risen out of the ashes of glam and pub rock . They had formed in the bar of the famous Marquee club in Wardour Street in London's West End...
Once they were a band, and had run through a few rehearsals in the cellar of the Marquee, they were ready to record a demo......
(http://nigelgoodall.co.uk/albums/stormtrooper/im-a-mess/)
why did this journalist choose past perfect for" form and disbanded?".I think He could have used past simple .It is not because it happens before the demo recordings (they disbanded after releasing their demo ) is it only to emphasize the moment the band existed (from the creation to the split) .
Or may be that it is not past perfect for disbanded but past simple. But if it is the case it is obvious that the creation of the band happened before the split so there is no reason to use past perfect .
ps I understand the use of had risen ( because of the completion of the action) and had risen gives the impression that punk rock did not come in one day but took some time to arrive