While most method books stick to I-IV-V chords, Gillock throws in ii-V-I progressions, modal mixtures, and chromaticism. Students absorb jazz and 20th-century harmony by ear, which makes them better sight-readers and improvisers later.
If you search for the it is almost certainly a piano teacher doing the searching. Here is why this book is a pedagogical masterpiece: william gillock recital collection pdf
Department of Integrative Biology, Oregon State University, OR 97331, USA