Sentence:  Those persons who were lucky enough to see and hear the performance of his work at the Brest-Silevniov Festival in August , 1916 , will certainly welcome his return to public notice ; and it is not unlikely that , even as the great Bach lay dormant for <WSD>so</WSD> many years , so has the erudite , ingenious SalFininistas passed through his `` purgatory '' of neglect . 
Meaning of the word marked with <WSD> tags:  to a very great extent or degree