Music theory is the study of theoretical frameworks for understanding the practices and possibilities of music. The Oxford Companion to Music describes three interrelated uses of the term "music theory": The first refers to the "rudiments" needed to understand music notation such as key signatures, time signatures, and rhythmic notation; the second is a study of scholars' views on music from antiquity to the present; the third is a sub-topic of musicology that "seeks to define processes and general principles in music". The musicological approach to theory differs from musical analysis "in that it takes as its starting-point not the individual work or performance but the fundamental materials from which it is built."