In Theory: '25 or 6 to 4' by Chicago

In Theory: "25 or 6 to 4" by Chicago

By Anthony Martinez

We should get the big question out of the way first: What does "25 or 6 to 4" mean? The somewhat inscrutable title of Chicago's classic 1971 hit, written by Chicago's organist/vocalist Robert Lamm, refers to the time of day: 25 or 26 minutes until 4:00 in the morning. The lyrics paint a picture of a weary songwriter who has stayed up far too late and is debating whether to keep working or go to bed. Now you know!

Let's dig into the theory at play in this track. The song's iconic main riff features a repeated descending figure in A minor.

Am – Am7/G – Am6/F# – F – E

The first three chords of the progression look like they have a lot going on, but it's really just an A minor vamping over the descending A-G-F# movement in the bass. The chromatic motion continues from F# to F (the VI chord), which in turn leads very smoothly into E (the V chord), so fundamentally the progression we have is:

i - - - - - VI – V

The choruses deviate briefly from this pattern, moving toward the relative major key of C Major:

F – C – G – F

Cm: IV – I – V – IV

Am: VI – III – VII - VI

Lead guitarist Terry Kath really shines throughout this song; his stellar guitar work keeps things interesting, even after nearly five minutes of playing over that same A-minor vamp. While most of the lead material is rooted in the familiar rock 'n' roll guitar world of the minor pentatonic and blues scales, the chromatic aspects of the main riff allow him to venture into the more exotic melodic terrain of the Dorian and melodic minor. Kath foreshadows a lot of what will be happening in the solo during the second verse, peppering in some tasty licks before he lets it rip. Give his solo a listen as an isolated track:

Pay close attention to how Kath uses register to provide shape to his solo, which begins at 1:58 – starting low and then rising and falling over time, creating an overall sense of rising intensity over the course of the solo, with localized peaks and valleys in the playing to maintain interest. It's like good storytelling; the whole story has an arc to it, but each sentence and each paragraph needs to be interesting on their own to keep the listener engaged.

As is common with the fundamentally blues-rock guitar style, Kath employs a lot of legato passages, where notes flow smoothly into each other using hammer-ons and pull-offs, and compound bends, where a pitch is bent multiple times over the course of a single sustain. Both these techniques give his playing a more vocal, soulful quality than it would have with uninflected notes.

Terry Kath is once said, "I'm too busy playing to worry about the movement or the fingerboard. I just listen to it as it's all happening." May we all be able to achieve that level of flow in our playing!

Anthony Martinez has been a developer on the Rocksmith team since 2012. He received his B.A. in Jazz Performance and Certificate in Music Business from San Francisco State University.