This summary video should be a truncated version of all material covered in the class. This is not intended as a teaser, but rather an actual reference for any attendee to watch afterward so no information will be forgotten. Think of this summary video as a quick recap of all content covered in the class.
These videos will be available for attendees to purchase as an upsell after the class or as part of a bundle when signing up. A professionally executed video will add incredible value to a class and be much easier to promote. By extension, those classes with excellent video summaries will likely fare far better than those that are poorly executed.
If this is a repertoire class, this may be running through covered songs and song elements within each (form, chords, etc.) If this is an improv class, this may be a short recap of concepts and example demonstrations. If this is a music history class, this may consist of summarizing the historical turning and flash points, important artists and their influence, styles, and sociopolitical influences throughout the time periods covered.
Please consider writing out the entire video to read off cue cards behind your camera, to avoid stalling and stumbling through any explanations. This will create the most professional delivery of information.