Copyright does not work that way. Copyright awards protections to a creative act.
If you use a computer to generate songs, there is no creative act, and no copyright.
If you copy a song someone else generated with a computer, there is no creative act, and no copyright.
If you independently write a song, and a computer independently creates an identical song, there is a creative act, and you own the copyright to the song you created (but the song the computer created is in the public domain).
If two people independently write the same song, then they both own the copyrights to their respective songs.
If there is not substantial creative expression by the user in the final output, then the output is in the public domain. And independent creation is a defense against copyright infringement claims.
"...authorship rights should go to the user when the user makes a very substantial contribution to the output. But when the user does very little and most of the output is left up to the AI machine, then it is less likely that the user may own the copyright in the output. " [CONTU 1974 - yes, 1974]
If you use a computer to generate songs, there is no creative act, and no copyright.
If you copy a song someone else generated with a computer, there is no creative act, and no copyright.
If you independently write a song, and a computer independently creates an identical song, there is a creative act, and you own the copyright to the song you created (but the song the computer created is in the public domain).
If two people independently write the same song, then they both own the copyrights to their respective songs.