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Music theory, Let It Be, track 9

One After 909

The Beatles · from Let It Be (rooftop concert, Jan 1969) · Lennon composition

A study in the dominant-seventh blues key and a cycle-of-fifths bridge.
The verse is B major built entirely from dominant-seventh chords (B7, E7, F#7), the blues idiom in which every chord of the key has a lowered seventh. The bridge climbs by fifths, E7 → B7 → C#7 → F#7, using C#7 as a secondary dominant of F#7.

Key B major, blues idiom Verse B7, E7, F#7 (1(7), 4(7), 5(7)) Bridge cycle of fifths with 2(7) as V/V Form 12-bar-adjacent verse, bridge, solo

One After 909, plain words

The home key is B major, played in the blues style, so every main chord has a “7” added to it (B7, E7, F#7).

Adding the 7 to every chord is what makes the song sound bluesy instead of pop-major.

The three main chords are the same three used in a 12-bar blues: home, four-up, five-up.

In the bridge a new chord appears, C#7. It is not from the home key; it is used to point at F#7 from a fifth above, a classic move called a secondary dominant.

The chords climb by fifths in the bridge: E7 to B7 to C#7 to F#7, each one pulling the next along.

To see the exact chords and key, open Pollack or Isophonics.

How to read this page. The chords below are from a public transcription, in B major with a blues-style dominant-seventh palette.
The song was written in 1957 and recorded in 1969 for the rooftop concert; harmonically the analysis treats it as a straight B-blues piece.

The theory

Key & tonal center

B major, blues idiom

The home key is B major, but no B major triad appears anywhere in the song. Every chord of the key is played as a dominant seventh (B7, E7, F#7), which is the defining sound of the blues idiom.
Adding a ♭7 to the tonic chord bends the harmony out of pop-major and into a blues color, without changing the actual key center.

The verse

A 12-bar-adjacent progression on 1(7), 4(7), 5(7)

The verse cycles through B7 (1), E7 (4), B7 (1), F#7 (5), B7 (1), which is a compressed version of the standard 12-bar blues shape. The three chords 1, 4, 5 are the primary triads of the key, all voiced as dominant sevenths.
The 5-chord (F#7) provides the strongest pull home; the 4-chord (E7) provides the plagal-flavored contrast.

The bridge

A cycle-of-fifths climb with a secondary dominant

The bridge runs E7 → B7 → C#7 → F#7, each chord a fifth above the previous. C#7 is not diatonic to B major; it is a secondary dominant, the “V of V” pointing at F#7 from a fifth above.
The bridge repeats the four-chord climb, then hands the harmony back to the verse. This is a classic pre-1960 rock-and-roll bridge shape.

The 2-chord

C#7 as V of V, not a diatonic 2m

In plain B major the 2 chord would be C#m (2m). Here it appears as C#7, a major-quality dominant seventh. That change turns the 2 chord into a temporary V-chord pointing at F#7, tightening the pull through the cycle of fifths.
The trick is the reason the bridge feels goal-directed instead of harmonically static.

Form

Verse, bridge, verse, solo, bridge, outro

The full structure is a three-verse-with-bridge form, plus a guitar solo over the verse changes, then a repeat of the bridge and an extended tag-out on B7, E7, F#7. No modulation, no key change, no borrowed chord outside the C#7 secondary dominant.
The whole song is B, E, F#, C# in dominant-seventh voicings, four chords total.

Key analysis

Key: B major, blues idiom (every key chord voiced as a dominant seventh).
Scale: B C# D# E F# G# A# (major); the ♭7 in every chord is the blues-idiom color.
DegreeChordNashvilleRoman
1B71(7)I7
2C#72(7)V/V (secondary dominant)
4E74(7)IV7
5F#75(7)V7

Nashville numbers

Chords sourced from a public transcription, in B major with a blues-idiom dominant-seventh palette.

Intro

1(7)B7

Verse (12-bar-adjacent)

1(7)B7
4(7)E7
1(7)B7
5(7)F#7
1(7)B7

Bridge (cycle of fifths, C#7 as V of V)

4(7)E7
1(7)B7
2(7)C#7
5(7)F#7

Solo (verse changes)

1(7)B7
4(7)E7
1(7)B7
5(7)F#7

Outro (tag)

1(7)B7
4(7)E7
5(7)F#7
1(7)B7

Reading the numbers: each is a scale degree in B. Plain = major, (7) = a dominant-seventh coloring. The whole song is four dominant sevenths: 1(7), 4(7), 5(7), and 2(7) used as V of V in the bridge.

Chord fingerings

All four chords are dominant sevenths (low E to high e; x = mute).

Confirm the specifics here

Pollack, "Notes On One After 909"

Prose analysis of the blues-idiom verse and the cycle-of-fifths bridge.

Open Pollack mirror →

Isophonics, annotations

Downloadable chord and key files (per-album zip that includes One After 909).

Open Isophonics →

HookTheory / TheoryTab

Roman-numeral function and melody for the verse and bridge.

Open the song page →

BeatlesFC

General Beatles harmonic-function paper (not per-song).

Open the paper →
Song 27 of the 1969-forward queue, ninth of Let It Be. Theory only, no production notes.
Chords are from a public transcription; exact bar-by-bar detail is at the linked sources. See the full queue.