Sentence:  Thoroughly modern in treatment , they are at the same time , full of simple sincerity which invariably characterizes genuine Negro folk-music and are by no means to be confused with the average ' Broadway Spirituals ' which depend for their racial flavor upon sundry allusions to the ' Amen Corner ' , ' judgement day ' , ' Gabriel 's horn ' , and a <WSD>frustrated</WSD> devil - with a few random ' Hallelujahs ' thrown in for good measure . 
Meaning of the word marked with <WSD> tags:  disappointingly unsuccessful