The first of these four clips was part of a previous post here with some other piano-related material, but now that the whole series is online, it seemed worth sharing again along with the companion videos.
With regard to Harris, we refer once again to that previous post, which said:
A native of Detroit, Harris (pictured) has run the gamut from swing to bop to modern jazz in his 85 years, performing with major musicians including Sonny Stitt, Illinois Jacquet, Coleman Hawkins, Dexter Gordon, Lee Morgan, Charles McPherson, Max Roach, and many more. He's also been heavily involved in jazz education, giving master classes at colleges and universities all over the world.These lessons were recorded in September, 2013, and feature Harris talking with fellow pianist Eli Yamin, who helps him discuss and demonstrate various points. You can see a playlist with all four videos in the embedded window below.
For some additional free educational resources about jazz theory, take a look at Jazz Theory, a downloadable book in PDF format written by Stuart Smith, professor emeritus in the department of music at University of Massachusetts Lowell.
For a breakdown of similar material in smaller, "bite-size" pieces, there's what amounts to a step-by-step tutorial at the website Jazclass, and also some handy reference pages pertaining to jazz theory at TheJazzResource.com