I like listening to the Lullaby rock covers of Queen, Def Leppard, and others. Sometimes musicbox music is also very helpful for regression. I just ask Alexa to do it and end up with a nice pleasing mix of classic music to music box chimes.
I like to listen to Disney songs during the day while at work. Keeps my little self happy. When I really want to regress I listen to kids songs or toddler tunes on Spotify. Seems generic but it works for me. At night baby lullaby music.
I just listen to the music I listen to while big, so right now lots of Oingo Boingo (and various other New Wave bands, but OB is my fave), Autoheart, They Might Be Giants (both their kids music and 'regular' music), and Tally Hall (who did the music for the Disney Junior show 'Happy Monster Band'). I also listen to a lot of Disney music, especially the music used in the theme parks (former CM, I miss being there!)
I have no idea why but some of Jimi Hendrix's songs really put me in a good place when I want to be little. Axis, bold as love, and little wing are my two favorites, from him. Jefferson Airplane and Pink Floyd, help me feel little too sometimes.
I like to listen to happier, upbeat, sing along type tracks. A lot of Disney, of course, but also just anything else I find uplifting and bouncy!
For night time music I like to listen to lullaby type music, soft and melodic. It's really easy to chill and settle into a cocooned blankie pile and let myself drift with my imagination into dream land...