Historically informed performance (also referred to as period performance, authentic performance, or HIP) is an approach to the performance of classical music which aims to be faithful to the approach, manner and style of the musical era in which a work was originally conceived.
It is based on two key aspects: the application of the stylistic and technical aspects of performance, known as performance practice; and the use of period instruments which may be reproductions of historical instruments that were in use at the time of the original composition, and which usually have different timbre and temperament from their modern equivalents. A further area of study, that of changing listener expectations, is increasingly under investigation.