If you already have a subscription to a streaming service, you can download the track for offline use within the app: Lullaby - Single by R3HAB - Spotify

: Often lists digital releases where you can find 320 kbps MP3 files. 2. Official Free & Promotional Downloads

Sometimes artists or labels release certain versions (like remixes) for free via promotional sites:

: R3HAB and Mike Williams often upload tracks here. While not all are downloadable, some remixes may feature a "Free Download" link in the description. 3. Streaming (Offline Listening)