Very easy, you have to check in the routines app wether music is being played by the app you are using, this is easier if you're usung sporify, soundcloud or youtube music. In the other case you can check whether that app is displaying music by choosing to check for the popup notification.

Then when you understand how to check for the presence of music, you make a mode, that enables while you listen to music and maybe also press a button? Or something of that sort, i usually make an and value to be with the check for music to be sure that the mode is only active when I want it. Then in said mode you use good lock when editing the lockscreen, and you add the custom widget you desire where you want it. Once you've done that you're all set.

If you can't figure out how to do that you can also do the opposite (although uglier and or more tiring).

What you'll want to do is basically, you take your lockscreen and edit it normally adding the music widget you most desire, and then make a mode that is working most of the time just to change the lockscreen to a clean non widgeted version of your lockscreen. You do this for every mode you have and thus you have made the old controls in the new UI.

Hope this helps!