This post is one I've been meaning to make for a long time. Below you will find my own definitions to terminology I use periodically.
A sacred act in music. The moment when energy, which exists without form, is formulated by, and transmitted through the performer(s). The energy is then received by an audience, whose response returns back to the performer(s). The performer(s) prepare for this activity yet they are guided in the act by inspiration (sprezzatura). The goal of this activity is a shared experience between performer(s) and audience.
Historically-Informed Performance (HIP)
Movement in 20th/21st Century classical music involving numerous aspects of performance. Musicians self-identifying in the HIP movement perform on period- and regionally-specific instruments (or copies of instruments) relating to a given work. Emphasis is placed on the understanding of past performance practices and contextual research. Any work from any time period can be subject to an historically-informed performance.
A musician who has undergone a reevaluation in their development. One who has gone through the traditional classical music upbringing and is later introduced to HIP. This reevaluation includes a period of time focused on developing skills on a period instrument (or instruments), study of primary sources relating to performance practice, period-specific contextual studies, as well as an analysis of the goals of that musician and how they relate to the goals of HIP.
Musicians who self-identify with the HIP movement but who have not undergone the above-mentioned reevaluation. Most often this musician plays a period instrument (or copy), or owns relevant equipment to perform with early musicians (baroque bow, gut strings, etc.). However, a period-instrument performer can have spent their whole development in HIP. Regardless of their introduction to the movement, period-instrument performers have not often fully considered the goals or merits of the movement and how they relate to their own. The technical level of these players can vary from amateur to world-class professionals.