 Quartet singers combined both individual virtuoso performances and innovative harmonic and rhythmic invention — what Ira Tucker Sr. and Paul Owens of the Hummingbirds called "trickeration" — that amplified both the emotional and musical intensity of their songs.By the 1940s, gospel music had expanded to members of all denominations prompting black gospel artists to begin tours and becoming full-time musicians.In this venture Sister Rosetta Tharpe became a pioneer, initially selling millions of records with her ability to drive audiences into histeria by sliding and bending her pitch as well as accompanying herself on steel guitar.