
I'm geniunely curious how arranging music and making eurobeat works.
From Odyssey's streams on youtube I noticed that he composes the music, sings and writes the vocals all by himself.
He only takes the arrangements of the Touhou Soundtracks to make fitting music.
But how does that work for other artists?
There are some tracks on the TEB series (and also on the SEB) series which have different persons for vocals, lyrics, and arrangenents!
Do these people interact with each other or does the lyrics writer just write down some lyrics and passes it to the vocalist who sings them and the arranger makes an eurobeat track in the end?
That doesn't sound right to me because how should the vocalist know that he should sing this part more aggressively or softly?
Or do they sit all in a music recording booth and come up with the whole song together?
In programming for example we never design the graphical user interface first. Instead we try to implement the programs core features and then we make our way around it.
But on Odysseys stream it seems like he starts from the beginning of a song to an ending with having the lyrics already provided.
I don't think that the arranger has the exact notes and tone sets already in his mind or written down, instead he makes them during the song.
There are also vocalless tracks (using just vocal sfx of other tracks) which basically have the arranger in the credits which I can imagine as just one person to sit in front of his desk and making music all by himself.
Am I completely on the wrong track? I'd be really grateful if someone could enlighten me here on how an idea of an eurobeat song makes it way to the final file.
Thanks in advance!

Sorry if the text is badly formatted, I wrote it during a bus ride on my phone.