What you're training
A cadential 6-4 is spelled like a tonic chord — C, E, and G — but voiced with G in the bass, the dominant's own scale degree underneath the tonic triad. On the page it looks like "home." To the ear it doesn't sound like home at all: it sounds like an ornamented dominant, tense and unresolved, that only lands once it steps down into the real V7 a beat later. This drill trains you to catch that mismatch between spelling and function.
Two levels, one skill
Level 1 asks the basic question: does the approach to the cadence go straight from IV to V7, or does a cadential 6-4 get inserted in between? Level 2 assumes you can already hear the 6-4 and asks where it lands in a longer, 4-chord approach — right after the first predominant (2nd chord), or one predominant later, delayed to the 3rd chord.
Go deeper
The I⁶₄→V formula in 19 real pieces → shows exactly how often composers reach for this exact setup before a cadence. The theory: strengthening endings with the cadential 6-4 → covers why this "false tonic" makes a cadence land harder than a plain V7 alone. The rest of how pieces end → is the wider lane this drill plugs into — authentic, plagal, and Picardy endings, now with the ornament that so often precedes them.
Where it fits
Comfortable with chord quality and chord inversions already? Cadential 6-4 is the next layer — the exact bass-vs-spelling trick a second inversion triad can play, right at the moment a phrase is about to end. The full drill ladder has everything else.