Dr. Tillis has been a member of the music faculties of Wiley College, Grambling University, Kentucky State University, Amherst College, and the University of Massachusetts. He is the author of a published textbook, Jazz Theory and Improvisation, and has written articles and lectured on African American music and jazz nationally and internationally.

In 1980, Tillis was named "Distinguished Lecturer" by the Chancellor of the University of Massachusetts. He served as a music consultant for the United States Information Agency and provided a three-week residency at Chulalongkorn University in Bangkok, Thailand, where he lectured, performed, and advised the Music Department in developing a major in jazz. He has also lectured at Carnegie-Mellon University, the University of Connecticut, Kentucky State University, Regis College (Framingham, Massachusetts), the Danforth Association, and in Japan, Mexico, and Russia.