Is a composer who arranges other composers’ works as Igor Stravinsky did a thief? What if the works he arranges are his own? Is he less creative for doing this, as Harry Partch did? And what about Broadway composers, who typically hand over their lead-sheets to arrangers? Who is the principal creative contributor, composer or arranger? And how judge the member of a rock band who brings the equivalent of a lead sheet to the band to serve as a springboard for group improvisation? Moreover if an improvising group uses someone’s else creative work as a source where do you draw the line between composing and arranging? And the Baroque Era common practise of basing a cantata on someone’s else hymn or chorale? Should Bach be accused of plagiarism?
Does motivation justify any of these above-mentioned judgments? Is our legalistic society the reason any of this becomes a matter for lawyers and courts to decide? Or ASCAP? Or even the public media?