Video can be used in several ways in instrumental teaching, depending on the age of the student and the stage of learning they are at.
In lieu of a performance; As I only have a handful of private students, performance opportunities are difficult to come by as I can’t arrange for a concert or soiree every term. Instead of this regular performance, I ask that my students prepare a piece that I can record and then post on youtube for the students’ friends and family to view. The pressure of recording mimics the stress of performing in front of an audience (although in a much less stressful way) and demonstrates to the student the difference between being able to play a piece well, and being able to deliver a flawless performance on demand. Recording a performance in this way also allows the student to share their achievements with people far away, and to store their performance to look back on.
As a lesson tool; Every teacher provides feedback in lessons, but showing is always better than telling, and recording is a great way to show a student how they are playing, and identify areas that need improvement. Initially this is a teacher-led exercise, pointing out the mistakes. Gradually this can lead to the student reviewing the recording with teacher support, and finally the student can do this as a solo exercise, either in the lesson or as part of their at-home practice.
I have a channel on youtube where I post videos for my students performing. I always get parent permission before posting any videos of students online. If you like go and have a look at my little stars! http://www.youtube.com/channel/UCvBY510vTnG_LKqROfsdFsg?feature=watch