Led Zeppelin, in 1968. Photograph by Dick Barnatt/Redferns/Getty

Legal cases involving claims of musical plagiarism often lead to strange eruptions of musicological discourse in the halls of justice. Not long ago, the heirs of Marvin Gaye alleged that Robin Thicke and Pharrell Williams’s song “Blurred Lines” infringed upon the copyright of Gaye’s “Got to Give It Up.” A typical passage from the court documents: “[The defendants] argue that, as a matter of law, the 6-1-1-1 hook in ‘Blurred Lines,’ which is in the key of G and set to an E chord in the first measure and an A chord in the second measure, is not similar to the 6-1-2-1 hook in ‘Got to Give It Up,’ which is in the key of A and set to an A7 chord.” The jury was unswayed by such strict formalism and instead embraced a more holistic view, according to which—in the words of a prior ruling involving Mariah Carey—“no approach can completely divorce pitch sequence and rhythm from harmonic chord progression, tempo, and key, and thereby support a conclusion that compositions are dissimilar as a matter of law.” Although the case is still in litigation, the jury made a preliminary award of $7.4 million to Gaye’s family. And they say that music education is irrelevant.

The latest case is Michael Skidmore v. Led Zeppelin et al., and one can only hope that it ends up before the Supreme Court, so that Justice Ruth Bader Ginsburg can at long last get the Led out.* Skidmore represents the estate of Randy Craig Wolfe, a.k.a. Randy California, the guitarist of Spirit, a Los Angeles band whose discography includes “The Family That Plays Together” and “The Twelve Dreams of Dr. Sardonicus.” The suit claims that the finger-picking opening of Led Zeppelin’s 1971 song “Stairway to Heaven,” the stuff of a million teen-age guitar lessons, is taken from Spirit’s 1968 instrumental “Taurus.” The plaintiff cites the expert testimony of Alexander Stewart, a professor of music at the University of Vermont and a self-described “forensic musicologist,” who argues that the two songs “feature the same chords during the first three measures and an unusual variation on the traditional chromatic descending bass line in the fourth measure.” Stewart also states that both songs exude “a decidedly ‘classical’ style, particularly evoking a Renaissance atmosphere.” The defendants respond by positing that “the descending chromatic bass line is a centuries-old, common musical element not entitled to protection.” Judge R. Gary Klausner, in sending the case to trial, seemed persuaded by the plaintiff’s analysis, commenting that the “descending bass line is played at the same pitch, repeated twice, and separated by a short bridge in both songs.”

The defendants certainly have a point about the longevity of that bass line. In my book “Listen to This,” I devoted a chapter to the history of what is often called the basso lamento—a ground bass that falls, step by chromatic step, from the tonic note to the dominant. It arose in sacred and operatic music of the early seventeenth century, and proliferated all over music of the Baroque; two classic instances are Dido’s Lament, from Purcell’s “Dido and Aeneas,” and the Crucifixus from Bach’s B-Minor Mass. (See this page for many more audio examples.) The pattern became less common in the Romantic period, but it returned to fashion in pop music of the twentieth century, and particularly in songwriting of the nineteen-sixties and seventies. In the audio below, you can hear four examples in sequence: “Chim Chim Cher-ee,” from “Mary Poppins”; the Beatles’ “Michelle”; the Eagles’ “Hotel California”; and Bob Dylan’s “Ballad of a Thin Man.”

Audio: The basso lamento

What’s more, there are fundamental differences between “Taurus” and “Stairway to Heaven.” In the first, the lower voice descends by chromatic steps while the upper voice repeats notes of the tonic triad (A minor), rather like the opening of “Michelle.” In “Stairway to Heaven,” also in A minor, the lower voice descends by half-steps while the upper voice ascends—up an octave to an A and then further up to B and C. Such contrary motion against a falling chromatic line itself has many precedents, from Dido’s Lament to “My Funny Valentine”—and a YouTube user points out a resemblance to a seventeenth-century sonata by Giovanni Battista Granata. For a moment, “Taurus” and “Stairway to Heaven” do sound the same, but they quickly go their separate ways. Although Judge Klausner would probably rule the point immaterial, it might be added that “Stairway to Heaven” is a variegated tour-de-force of a song while “Taurus” is hazily inert.

As for the accusation that Led Zeppelin plagiarized Spirit’s “classical” atmosphere—the suit specifies “the presence of acoustic guitar, strings, recorder/flute sounds, and harpsichord”—this conveniently overlooks the fad for Renaissance and Baroque sounds in rock of the psychedelic era. Walter Everett, in his book “The Foundations of Rock,” lists dozens of rock-and-roll harpsichords, beginning with the Beach Boys’ “When I Grow Up (To Be a Man).” Recorders appear in the Rolling Stones’ “Ruby Tuesday” and the Beatles’ “The Fool in the Hill,” among others. In the Left Banke’s 1967 song “Walk Away Renée,” you hear a descending chromatic pattern in combination with flute and harpsichord—evidence that “Taurus” is more imitation than innovation. Also, there is no harpsichord in “Stairway to Heaven.”

To be sure, Led Zeppelin has a long history of what might be politely called musical appropriation. Their 1968 anthem “Dazed and Confused,” with its monumental descending-chromatic riff, draws so liberally from Jake Holmes’s song of the same name that it’s a wonder Holmes waited until 2010 to file a lawsuit. (It was apparently settled out of court, with terms undisclosed. Holmes is, by the way, an interesting guy.) Claims on behalf of Howlin’ Wolf, Willie Dixon, and Anne Bredon were strong enough that their names have been added to the credits on Led Zep reissues. Given that history, it’s easy to believe that Jimmy Page encountered Spirit’s song—the suit offers evidence that Page knew the band’s music—and used it as a point of departure.