Marvin Gaye’s family have taken a highly unusual step in their copyright battle over Robin Thicke’s ‘Blurred Lines’ – submitting their own audio mash-up to the court.

The story so far: after the release of Thicke’s chart blockbuster ‘Blurred Lines’, Gaye’s children publicly suggested that the single was an unlicensed rip-off of their father’s 1977 track ‘Got To Give it Up’. In August 2013, Thicke, Pharrell Williams and T.I. filed a pre-emptive lawsuit against the family, then allegedly offered the family a six-figure settlement to ward off further legal action – an offer the Gayes refused. The family subsequently launched a countersuit of their own, claiming that a “Marvin Gaye fixation” runs throughout Thicke’s entire body of work, and hired a musicologist to plot the similarities between both tracks.

As Billboard report, Gaye’s estate have now filed their summary judgement papers, outlining their arguments and their grievances. As part of their submission, they’ve taken a largely unprecedented step: providing an audio mash-up of the two tracks to demonstrate “concrete musical illustrations of the substantial similarities” between the two tracks.

The recording sees the ‘Blurred Lines’ vocal material playing over the ‘Got to Give It Up’ instrumental, and vice versa. According to the document, “this material sounds like a perfect, natural match because it blends sonically”. The document notes that both songs have “two-measure phrases, which leave space in the middle of each of the bars, rhythms, and points of harmonic arrival. This is not simply an element of a genre, as it is unusual to have bass lines in R&B that leave this much space in the middle of the bar.”

The family have also dug up various interviews with Williams and Thicke to support their case. Among the examples given are an interview where Williams claims to have pictured himself as Marvin Gaye when making the song, and another where Thicke telling Pharrell he’d “love to make something like [Got To Give it Up]”.

That’s not all: also take umbrage at Thicke and Williams’ claims that the family had “smelled money”, noting that they were the ones who were sued first: “Not only was it, therefore, Thicke and Williams who actually ‘smelled money,’ but it was they who then played the role of bully by suing Marvin Gaye’s children when the Gaye children had the temerity to question why their father was not credited, or why ‘Got to Give it Up’ was not licensed, betting that the Gaye children would not have the will or resources to fight this battle. Thicke and Williams bet wrong, and they will now have to face the consequences of their misjudgment and their blatant copyright infringement”

The judgement papers are available over at The Hollywood Reporter. A decision is expected in the coming months, and a jury trial will begin on February 10.