Question: What are the three chords that McCartney plays on?
About the article "Hey Jude", section "Composition and structure".

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Adding a minor seventh to a major triad creates a "dominant" seventh (denoted V7).
In music theory, the "dominant seventh" described here is called a major-minor seventh, emphasizing the chord's construction rather than its usual function.
Dominant sevenths are often the dominant chords in three-chord progressions, in which they increase the tension with the tonic "already inherent in the dominant triad".
The dominant seventh discussed is the most commonly played seventh chord.
An A-major I-IV-V7 chord progression A-D-E7 was used by Paul McCartney in the song "3 Legs" on his album "Ram".</ref>These progressions with seventh chords arise in the harmonization of major scales in seventh chords.</ref> 
 A brief overview Chords in music theory.
The musical theory of chords is reviewed, to provide terminology for a discussion of guitar chords.
Three kinds of chords, which are emphasized in introductions to guitar-playing, and .</ref> are discussed.
These basic chords arise in chord-triples that are conventional in Western music, triples that are called three-chord progressions.
After each type of chord is introduced, its role in three-chord progressions is noted.
Intermediate discussions of chords derive both chords and their progressions simultaneously from the harmonization of scales.
The basic guitar-chords can be constructed by "stacking thirds", that is, by concatenating two or three third-intervals, where all of the lowest notes come from the scale.</ref> 
"Hey Jude" begins with McCartney singing lead vocals and playing the piano.
The patterns McCartney plays are based on three chords: F, C, and B-flat (I, V and IV); the second verse adds accompaniment by guitar and a single tambourine.
The main chord progression is "flipped on its head" for the coda since the C chord is replaced by E-flat.
Author Tim Riley notes, "As Ringo offers a restrained tom-tom and cymbal fill, the piano shifts downward to add a flat seventh to the tonic chord, making the downbeat of the bridge the point of arrival ('And any time you feel the "pain"')."
At the end of each bridge, McCartney sings a brief phrase ("Na-na-na na ...") and plays a piano fill which leads to the next verse; the phrase McCartney sings serves to "reorient the harmony for the verse as the piano figure turns upside down into a vocal aside."
Additional details, such as tambourine on the third verse and subtle harmonies that accompany the lead vocal, are added to sustain the interest of the listener throughout the four-verse, two-bridge song.
The verse-bridge structure of the song persists for approximately three minutes, after which the band leads into a four-minute-long coda.
During the coda, the rest of the band, backed by an orchestra that also provides backing vocals, repeats the phrase "Na-na-na na" followed by the words "hey Jude" until the song gradually fades out.
"Time" magazine described the coda as "a fadeout that engagingly spoofs the fadeout as a gimmick for ending pop records."
Riley notes the repeated chord progression of the coda (I-VII-IV-I) "answers all the musical questions raised at the beginnings and ends of bridges," for "The flat seventh that pose dominant turns into bridges now has an entire chord built on it."
This three-chord refrain allows McCartney "a bedding ... to leap about on vocally", so he ad-libs his vocal performance for the rest of the song.
Riley concludes that the song "becomes a tour of Paul's vocal range: from the graceful inviting tones of the opening verse, through the mounting excitement of the song itself, to the surging raves of the coda."
In the televised documentary "The Beatles Anthology", McCartney, Harrison, and Starr are shown relaxing on a blanket outside.
Starr asks McCartney what he wrote in India and McCartney answers, "I Will."
Then Harrison begins playing this on his ukulele while he and McCartney harmonize with it. 
For the standard tuning, there is exactly one interval of a third between the second and third strings, and all the other intervals are fourths.
The irregularity has a price.
Chords cannot be shifted around the fretboard in the standard tuning E-A-D-G-B-E, which requires four chord-shapes for the major chords.
There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings.
In contrast, regular tunings have equal intervals between the strings, and so they have symmetrical scales all along the fretboard.
This makes it simpler to translate chords.
For the regular tunings, chords may be moved diagonally around the fretboard.
The diagonal movement of chords is especially simple for the regular tunings that are repetitive, in which case chords can be moved vertically: Chords can be moved three strings up (or down) in major-thirds tuning and chords can be moved two strings up (or down) in augmented-fourths tuning.
Regular tunings thus appeal to new guitarists and also to jazz-guitarists, whose improvisation is simplified by regular intervals.
On the other hand, 5-6 string open chords ("cowboy chords") are more difficult to play in a regular tuning than in standard tuning.
Instructional literature uses standard tuning.
Traditionally a course begins with the hand in first position, that is, with the left-hand covering frets 1–4.
Beginning players first learn open chords belonging to the major keys C, G, and D. Guitarists who play mainly open chords in these three major-keys and their relative minor-keys (Am, Em, Bm) may prefer standard tuning over many regular tunings, On the other hand, minor-thirds tuning features many barre chords with repeated notes, properties that appeal to acoustic-guitarists and beginners.