Disclaimer: this question is not about copyright. I am trying to understand why the voice melodies of the two songs are so similar. I thought the chord progression could be classical, and that there could be a theoretical explanation for the melody.
Some time ago I noticed that the second opening theme of the anime "Your lie in April" has a part of roughly 20 seconds that is nearly identical to another part of the famous japanese opening of Dragon ball GT ("Dan dan kokorohitareteku..."). The chords are essentially the same, and the voice notes are almost the same. Here are two links to Youtube videos that point to the correct minute (from those spots, the relevant part lasts roughly 20 seconds):
Your lie in April (2nd opening theme) 0:45 - 1:04
Dragon ball GT (opening theme) 0:25 - 0:47
The chord progression (transposed in D major (?)) is:
G A F#m Bm(7) Em F#m Bm D(7)
(with a variant that starts with Em instead of G in the second song; I am not sure about the 7's, hence the parentheses). This pattern is repeated two times in "Dragon ball GT" and almost two times in "Your lie in April". I guess there is no need of saying, but the second song is half tone above the first one.
I am reasonably sure the first just copied from the second (because of the melody, not just the chord progression), but I also thought that there could be a small chance that this is not the case. In particular, I have two questions to ask:
- Is the chord progression something recurrent/classical, that maybe both songs took from somewhere else? (For this, someone pointed me to this famous progression, although this explains only the first 4 chords).
- Given the chord progression, do you think the notes the voice can/should follow are in a sense "forced by", or a natural consequence of the underlying chords? Or instead do you think there is enough freedom in the voice melody to conclude that one took inspiration from the other beyond any reasonable doubt?
Explanation to the second question: the voice melody in the first song follows the chords quite strictly; I tried to sing the same lyrics with different notes that still match the notes of the underlying chords, but I did not find any natural alternative without unpleasant jumps between the notes. Also, basically the melody is simply descending for most of the time. This makes me think that maybe the melodies matching in the two songs could be not that strange after all.
I have a basic understanding of how notes and chords work, but I am not a musician, and for both questions I think it is needed some experience and knowledge. Also, I am new to this site and I hope the question suits the site (as you can see, mine is a theoretical interest, even though motivated by anime openings :) ).