On Thursday, Led Zeppelin guitarist and songwriter Jimmy Page gave a remarkable declaration in court where he admits to discovering a copy of Spirit's first album in his record collection. He's currently fending off a lawsuit brought by the heirs of Spirit's own guitarist, Randy Craig Wolfe, who contend that the famous song "Stairway to Heaven" derived from a 2-minute, 37-second instrumental titled "Taurus" from Spirit's 1968 album.

"I had not previously seen it in my collection and do not know how or when it got there," states Page. "It may well have been left by a guest. I doubt it was there for long, since I never noticed it before. But, again, I know I did not hear Taurus until 2014."

In conjunction with this declaration — as well as one by Led Zeppelin singer Robert Plant — the band has brought a motion for summary judgment to a lawsuit that was first filed in Pennsylvania before moving to California. The motion demands dismissal of an action that alleges a "falsification of Rock N' Roll history," specifically that "any reasonable observer, when comparing 'Taurus' and 'Stairway to Heaven,' must conclude that — at the very least — significant portions of the songs are nearly identical."

The key aspects of the motion involve not a fight to contend the songs aren't similar, but rather a consequential argument why the Randy Craig Wolfe Trust is in no position to bring a lawsuit in the first place.

Most notably, Led Zeppelin argues that Taurus was a "work for hire," meaning Wolfe himself never enjoyed copyright to his song. The basis here is that in 1967, Wolfe entered into a recording contract with Ode Records and a songwriter contract with its affiliate Hollenbeck Music, where it was agreed that Wolfe was a "writer for hire... with full rights of copyright renewal vested in [Hollenbeck]."

If that argument doesn't work — and it's a contention that is sure to be watched by other musicians working during the dawn of the rock era — Led Zeppelin next moves onto a second line of attack: Wolfe waived his claim in 1991, when during an interview he was asked about "Stairway" (others have long noted the similarity of the two songs), and responded, "If they wanted to use [Taurus] that's fine," and "I'll let them have the beginning of Taurus for their song without a lawsuit."

Argument #3: The 43 years between the time that "Stairway to Heaven" came out and the filing of the lawsuit rises to laches, meaning a delayed lawsuit that have a prejudicial effect on defendants. Nearly two years ago, in a Supreme Court decision that dealt with the famous Martin Scorsese film Raging Bull, the high court held that the equitable defense of laches can't be invoked to preclude damages claims brought within the applicable three-year statute of limitations; however here, the Led Zeppelin defendants say this doesn't mean that laches doesn't remain a viable affirmative defense.

If the above three arguments fail, then the judge may get to addressing the similarity of the songs. Here's a listen of "Taurus":

Led Zeppelin argues, "The similarity between 'Taurus' and 'Stairway' is limited to a descending chromatic scale of pitches resulting from 'broken' chords or arpeggios and which is so common in music it is called a minor line cliché... There is no substantial similarity in the works’ structures, which are markedly different. Neither is there any harmonic or melodic similarity beyond the unprotected descending line. Rather, straining to find something, the plaintiff’s expert argues that 'Stairway' and recordings of 'Taurus' have only five of the six chords in a centuries-old work — part of public domain material is still public domain material — and that both have the unprotected sequence of notes in a minor scale, A, B and C."

Here's the full summary judgment motion for more here.

If the judge reaches the point of comparing both songs, it will be influenced by a determination of a concept in copyright law known as the "inverse-ratio rule" where lots of access to a song necessitates less proof of similarity.

That's where Page's testimony comes in. The defendants argue that "Taurus" was not "widely disseminated" as it was not released as a single nor played on the radio. More importantly, they say there is no "chain of events" establishing that Led Zeppelin's members heard the Wolfe song.

In the lawsuit, Wolfe's heirs say that Led Zeppelin in its earliest days once opened up for Spirit on tour and that Page may have heard it before his 1971 recording session. The defendants say the evidence is undisputed that the two bands "appeared at the same venue on the same day only three times," and that Spirit performed its most recent songs, not "Taurus." Additionally, the defendants say that quotes attributed to Jimmy Page "as liking Spirit's albums and performances" is both hearsay and not proof he heard the particular song in question.

Page states in his own declaration (see in full below) that "Stairway to Heaven" was created independently, "with the intention to create a long work, with multiple different parts, that would unfold with increasing complexity and speed..."

He also discusses some of the musicians and songs he was familiar with at the time — the Beatles, "Cry Me a River," "Chim Chim Chiree," "Ice Cream Dreams" — that employed a similar descending line guitar concept.

After discussing the happenstance that the bands played together and how it was possible that he did not hear them perform live, he discusses his record collection — which included the song in which he's now accused of plagiarizing.

"I have several thousand albums of many different kinds," he says. "They include albums I purchased, albums people gave me and albums that were simply left at my home. Also, like a book collector who never gets around to reading books they collect, I have never listened to many of the albums."

(Here's Plant's own declaration.)