Baby playlist (What Frequency)

I started making my baby playlist and it started off with fun and happy songs and I’ve decided I probably don’t want that. I want something more Zen and super calming. Now I found that - it’s mainly synth frequencies. I’m now thinking about what frequency is good to control the energy in the room. For all the mama’s that are into that kind of thing. Are there any thoughts on what type of frequency I should look for in my calming zen music? What’s on your playlist?