TL;DR: In this paper, the authors support the idea that the cadential six-four is not a mere dominant with two non-chord tones, but a unique bi-functional chord which embodies a conflict between tonic and dominant.
Abstract: In this article I support the idea that the cadential six-four is not a mere dominant with two non-chord tones, but a unique bi-functional chord which embodies a conflict between tonic and dominant. This concept allows the explanation of all possible appearances of the cadential six-four in the music literature.