Please, how can I set my gmusic browser to start with my PC start up, but just to the tray?

go to settings > layouts > show tray icon > start in tray.

I have no item "start in tray" there.

That option is only available in the development version, available in git. Follow instructions here to get it.

There is also the "-hide" command line option, available even in v1.0.x, that will hide the main window on startup.

Thank you very much, the problem is solved. I used the -hide command. Perfect.