The One Piece is the music of the world
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If this report is true, then I think the One Piece could be the music of the world.
Between Nika and his own soundtrack, WCI being heavily musical themed - let's not forget that Big Mom had a road poneglyph and was trying to use Pudding, someone Blackbeard currently has (so we know she will be important at some point) - Imu having his own sound track that is like an evil version of Nika's but with Big Mom's Homi (a power based on souls) styling to it, and now Zaza being another god named after the sound of the music that represents them, I think Oda is drawing heavy parallels here.
Brook is a musician - and another character with soul based powers - and sings Bink's Brew alot. The Straw Hats always party with music everytime they win and leave an island. Its been heavily theorized Luffy wants to have one big party at the end of his journey, and even Onigashima raid was centered around basically one giant music festival.
So maybe the reason Roger laughed, is because he was witnessing this music.
I also saw someone make a comparison to Lord of the Rings, and I thought this was fascinating.
In Tolkien's Legendarium, Eru Illuvitar and the Valar sung the music of Ainur. However, one of the biggest Valar, Melkor, did not want to. He wanted to create his own and find the flame Imperishable to overpower Eru. He could now, however, as the flame existed within Eru. So, Melkor sowed discord within the song instead, and this discord is what led to corruption and evil existing within Arda - as evil cannot create, it can only corrupt.
What if the gods from the 2nd or the 1st world sung their own song of Ainur, and Imu was Melkor, he wanted the flame imperishable (the Mother flame) to conquer the world, but could not, so instead using his devil fruit, he sowed a discord into the song and corrupted the world via his Domi Reversi / Holy Knight sigils and subsequently the Celestial Dragons and World Government. He couldnt create, so he instead corrupted, and the One Piece is that original song of joy and happiness that existed before Imu did what he did.
Not a perfect theory as this is off the top of my head and not something I sat on for days or something, so I know it's definitely flawed, but I thought it could be interesting.