Non-cadential use of 6/4 chord

Question

I guess the 6-4 chord in common practice music is typically seen as a "cadential" 6-4, used to embellish the chords around it by means of bass arpeggiation.

In rock music, however, a I chord in second inversion could be part of a descending bass-line progression.

The issue is that (in the key of C major for example) a C major chord with a G in the bass sounds unstable--not the best start to a verse progression (ex. I64-IV-iii-V64).

Is there a way to lead into the I64 chord or voice it a certain way so that it is more stable/rich? Or is this chord typically avoided because of it's inherent instability and I should look at a progression such as I-I42-vi-I64 instead?

Thank you.

Answer 1

From the point of view of composition, you may want to initiate your verse with the I, and then see if you might use a V/V (D, F#, A) in whichever inversion to get the leading tone back to the G in the bass line. A V7/iii or VII7/iii could also give you that F# leading tone into your inverted I6/4 in the bass, and allow you to suspend the C tonic (perhaps in octaves) across another part or two. This is essentially just a tritone resolution to the key of G, which may fool the ear and make the inversion feel more appropriate.

Perhaps use the keyboard to play the C in octaves (which are inherently stable) when you arrive back at the one to offset some of the inherent instability of the inversion.

Be interested to hear what you come up with.

EDIT: Here's a resource that discusses secondary dominants in the key of C. http://www2.siba.fi/muste1/index.php?id=87&la=en

Answer 2

There are at least three "textbook" ways to use a 6/4 chord in common practice harmony, apart from the cadential 6/4.

Of course outside of common practice harmony, there is no limit to what you can do except your musical imagination.

In a passing 6/4 the bass note functions as a passing note between two stable chords.

In a pedal 6/4 the bass note remains on one pitch while the chords above it change.

In an arpeggiated 6/4 the chord remains the same, but in different inversions.

See http://www.musictheoryteacher.com/pb/wp_94176fc5/wp_94176fc5.html for examples.

Answer 3

If the voice leading works, one can put a I64 chord where a iii6 might be expected. This is common in early pre-classical occurrences of the Pachelbel Canon chord pattern: I,V6,vi,iii,IV... vs I,V6,vi,I6,IV...; step 5 in the bass walks from step 6 to 4 so this might be considered a "passing six-four." (Mostly I've seen the passing 64 when moving from IV to IV6 or I to I6 or back: it's the same movement from vi to IV.

The I64 differs in only one note from the ii6. Some sort of 6-5 or 5-6 motion could create a 6-4.