All good suggestions (I particularly like Mindfulness). I have also found the theta field (not free) useful.
The Dreamscape card in the Dreamweaver Card System is also helpful. It is designed specifically for the purpose of meditating and reaching deeper brainwaves.
I also have an unorthodox one: I find that when I connect to love before meditating, it’s easier to have a quiet mind and my meditation is always more fruitful. This field (in the last paragraph called The Love) teaches the mind how to create love “on command” (which is great for any life circumstance haha)
Happy meditating 