The song begins with those familiar acoustic guitar phrases—often repeated and often messed up by guitar students. Writer Richard Walser calls the beginning "reassuringly square" and it's true, the beginning guitar phrases follow a long-established classical music design. There are four phrases that are each four measures long, which are repeated until the electric guitar steps in. The rhythm is also as plain as you can get: simple eighth notes. The music here emulates the style of the baroque period in England (early 17th century). You can hear it in the flourishes that finish the phrases (especially in the measure right before Plant first starts singing), the pastoral timbre of the recorder, and in the contrapuntal melodies of the acoustic guitar. (Contrapuntal, roughly meaning, "point against point," is where two or more melodies are playing distinct from one another in a song.) In the arpeggiated opening lines you can hear the lowest notes descending downward (chromatically from A to F) while the highest notes in each phrase gradually rise (A to B to C).
From there the song moves away from these acoustic, pastoral tones by incorporating electric guitar and, later, drums. As the song moves on, it is interesting to think of music as moving stylistically through time in a kind of search… bringing us to the climax of the song, the guitar solo.
The solo is prefaced by what is called a fanfare. A fanfare is a short piece on horns to introduce royalty, to begin a military ceremony—or even to begin a news program (the horns at the beginning of The Daily Show, anyone?). The bright tonal quality of Page's guitar emulates this trumpeting, and the quick triplet chords that he plays further suggest that Page is imitating a fanfare. It's as if the wandering musical styles of the first half of the song have found some kind of hero — a guitar hero.
If the beginning of "Stairway to Heaven" embodies the folk, classical, and mystical influences on Led Zeppelin, Page's guitar solo represents all the contemporary influences on the band's rock sound. It is a melding of the emotional improvisation of blues tradition with the more psychedelic influence of Jimi Hendrix and contemporary British acts.
Jimi Hendrix gets a lot of the credit for the modern rock guitar sound, but perhaps just as important were The Kinks, whose song "You Really Got Me" featured one of the first successful usages of heavy guitar distortion. We can hear echoes of both in the sound of Page's guitar.
Like Hendrix and most rock guitarists today, Page never (intentionally) used complicated music theory or techniques in writing his songs. It is unlikely that Page cared that the final note of the first solo phrase is the sixth from the root—or that the solo is almost entirely in the pentatonic scale, a mainstay for rock guitar. But Page has always said that his guitar style has nothing to do with technique—he "deals in emotions." It makes sense then that his guitar solo in "Stairway" is an improvised one. Sound engineer Andy Johns recalled, "Jimmy had a little bit of trouble with the solo ... [he] hadn't completely figured it out. I remember sitting in the control room with Jimmy, he's standing there next to me and he'd done quite a few passes and it wasn't going anywhere. Then bang! On the next take or two he ripped it out."
"Dealing in emotions" as Page did with the solo harkens back to the improvisational blues influences on the group. Though Led Zeppelin played an important role in developing the heavy metal sound, over a third of their songs are acoustic and many of their hits were more blues than metal.
The song's hard-rock ending section builds upon the solo. Robert Plant's trademark screeching vocals join the fray while Page continues to throw in licks. This last verse section continues to use the A minor-G-F chord progression—something else that thousands of familiar songs use, this section ending on the F chord. Typically musical pieces end on the tonic—the root note of the key. "Stairway to Heaven" is in the key of A minor, so it should end with an A note. But the rock section doesn't. Instead the song finds its tonal resolution by coming full circle and ending with a single, simpler melody line: Plant singing, a cappella, "And she's buying her stairway to heaven."