I teach by Skype for a school that is a three-hour drive from where I live. It is not ideal, but better than no lessons at all. The better the equipment, the better the experience. I position my harp so that the student can see my hands on the strings, and the student does the same on their end. Sometimes the connection is not great, so there can be a delay in what you see and what you hear. It can be hard to judge sound and tone quality, when it is unclear whether it is the connection’s fault or the student’s playing. But you can correct hand position, rhythm and interpretation. It is best if the student can come occasionally for a live lesson.