The table to the left shows the most common uses of each kind of 6/4 (other uses within each category have been illustrated on previous pages). Notice that the bass is always doubled in the 6/4. This doubling can be used as a check that the voice leading is correct.

When using 6/4s in freer contexts than these short expansions of the fundamental harmonic progression, it must be remembered that cadential 6/4's always occur on strong beats and the others occur on weak beats (see examples to the left and from the literature throughout this chapter).

Also, largely because of the dissonant fourth against the bass which usually contracts to a third, it must be emphasized that these four general categories, cadential, passing, neighbor (or pedal) and arpeggiated, are the only ways 6/4's can be used. When harmonizing a melody do not use 6/4's indiscriminately or to provide an interesting bass line. Exceptions to these four uses in the literature are extremely rare.

The above caution notwithstanding, composers almost always use the cadential 6/4 when harmonizing a melody ending with scale degrees 3, 2 and 1 (with 3 and 1 on strong beats). Other harmonizations of this very common phrase ending may "sound fine" in the present day, but they are almost never used by composers of the common practice era. Students should therefore make a habit of using the cadential 6/4 to harmonize these notes.