August Kitko and the Mechas from Space (The Starmetal Symphony 1)

When an army of giant robot AIs threatens to devastate Earth, a virtuoso pianist becomes humanity's last hope in this bold, lightning-paced, technicolor space opera series from the author of A Big Ship at the Edge of the Universe.

Jazz pianist Gus Kitko expected to spend his final moments on Earth playing piano at the greatest goodbye party of all time, and maybe kissing rockstar Ardent Violet, before the last of humanity is wiped out forever by the Vanguards—ultra-powerful robots from the dark heart of space, hell-bent on destroying humanity for reasons none can divine.
But when the Vanguards arrive, the unthinkable happens—the mecha that should be killing Gus instead saves him. Suddenly, Gus's swan song becomes humanity's encore, as he is chosen to join a small group of traitorous Vanguards and their pilots dedicated to saving humanity.