Sentence:  He was thinking; but the glory of the <WSD>song</WSD>, the swell from the great organ, the clustered lights,nb..., the height and vastness of this noble fane, its antiquity and its strength—all these things seemed to have their part as causes of the thrilling emotion that accompanied his thoughts. 
Meaning of the word marked with <WSD> tags:  A musical composition with lyrics for voice or voices, performed by singing.