I’ve been using this for several years (bought a lifetime subscription when it was on sale). I use it nearly daily, and it’s very helpful. I have known for a long time that I focus better with some sort of instrumental music playing in headphones - lyrics kill my focus. I listen to a lot of jazz and film scores that I have in Apple Music playlists, so I can just start one and it’s good for 3-4 hours. Brain.FM gives me something additional to add to the mix, and I do think that it provides somewhat better focus than just regular music.
