Jipp that's quite right. Though the conditions between music and art differ.
With art you have possibly millions of ways you can portrait the same thing not only by medium (usually it is some kind of paper with us, so we stick at that), but also by the condition that every person has different muscle and bone conditions. Thus: A Mickey Mouse looks and looked fairly differently drawn by Walter Disney compared to a Mickey Mouse by Carl Banks though both drew the same character but in very different incarnation. Not only by decision but by chance. Thus the probability of copying the same character to the last detail is very improbable (which is why plagiarists in the art scene are both: Hated and sometimes pretty wealthy if they are good at selling "their" works without getting caught.
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Music though is a medium which is standardised western. Almost the whole world uses a notation form (which emerged around 1600 from a different notation form called "mensure" which itself is from ca. 1300). So it is a very old system which basically has two rules that are then again standardised: Tempo and pitch.
Pitch means that we have 12 notes within an octave, though there are 7 main notes that will be used through the whole course. If we take c-major it is always c d e f g h a and b (mi fa sol la si do and re in France). Which ALSO means: In this whole octave will always be 5 whole note steps and two half note steps (here from e to f and from b to c). Sometimes (or very often) componists use minor steps within this scale. The more "funky" (not the style, I'm not talking about music from the 1970's per se) the music is the more probable it will happen. Our modern scales though are all based on an A = 440 Hz. So as long as we don't get experimental in sound (like in newest music or veeeeery psychadelic stuff), we always have the same base.
The same goes with tempo: The biggest mostly used note is a "whole note", which can be halfed into two "half notes" which can halfed in "quarter notes" which can halfed into ...
Then we measure time in beats per minute and "voila" we have got the western scale system. And this western (european) system is used in pretty much everything: Of course european music, american music (no matter if "black" or "white", both use it, live with it, but do not fred dear brothers of colour: You did not have a choice!). My favourite asian bands use them as well, though they can be called "folk rock bands", but they use the european system. Then in middle eastern music, arabic music, south asian music ...
What I wanted to say with this: In music we only have a variety of 12 notes in combination to a (mostly used) variety of 9 note values. As such the usable amount of figures and themes are much more limited. This though of course isn't a sign to say that someone is free to use stuff he did not create just because of that.
Copying always was something people did, and your example @vothnthorvaldson was pretty good! The question though is: Where is the border of stealing compared to homage? I know for instance that Mozart used a theme of Bach's "Matthäus Passion" in his 42. Simphony. Probably as homage. Bach's own son (I think it was Wilhelm Friedemann) even wrote music in name of his father so he could pay bills (because of course compositions of his father had a much higher worth than Wilhelm's).
And then there is John Williams who pretty much LOVES using themes from Dvorak, Stravinsky and many others in his works (We can hear themes of both componitsts in both: "Jaws" and "War of The Worlds" for example).
Of course this is a topic to discuss about for many evenings (lol and I already did <.< like I said once: I am a musiciologist, that is all we do, lol) but I think I can say: Tracing art pretty much is like using the same theme by every note equally (hence ripping off). It's much easier to do so in music (and maybe even more obvious, I think, but maybe that is just me), but unfair it is both!
Sources:
- Listen here for Dvorak's 9th symphony, 4th movement. You can hear "jaws" at the beginning and if you keep listening you even hear Star Wars.
Not kidding! https://youtu.be/_9RT2nHD6CQ?t=2365
- And here for Stravinskys "Firebird". In this case: More Star Wars! https://youtu.be/MHmk7yccvws?t=2178
- Here is Gustav Holst's "Planets". First movement "Mars" shows us who the Klingons (Star Trel) got their icony movie-music, but Mr. Williams also took some uhm .. "inspiration". https://youtu.be/Isic2Z2e2xs
- War of Worlds (no, I mean The Rite of Spring by Stravinsky :-P) https://youtu.be/rP42C-4zL3w?t=209
Enough is enough now, I annoyed you lot enough already. 