Sentence:  The style of music generally used for creating <WSD>filk</WSD> is folk or popular music. That brings up one of the key points. Most, but not all, <WSD>filk</WSD> is created by "borrowing" the music of other songs and creating lyrics to fit the singer's particular circle of fandom. 
Meaning of the word marked with <WSD> tags:  Filk music.