Tonespace lets you play one note and intelligently augments what you’re playing with chords and arpeggios.
It connects via Midi (so to a synth or Garageband) and plays musically similar notes. Because it generates midi, you can “record” it and then use it in whatever DAW you are using.
Auroral radio emissions are associated with the Northern Lights or Aurora. The most intense of these emissions is a phenomenon called Auroral Kilometric Radiation (AKR). It is produced in the auroral zones at an altitude between 3000 and 20 000 kilometres.
From Wikipedia: I am sitting in a room is a sound art piece composed in 1969 and one of composer Alvin Lucier's best-known works.
The piece features Lucier recording himself narrating a text, and then playing the tape recording back into the room, re-recording it. The new recording is then played back and re-recorded, and this process is repeated. Since all rooms have characteristic resonance or formant frequencies (e.g. different between a large hall and a small room), the effect is that certain frequencies are emphasized as they resonate in the room, until eventually, the words become unintelligible, replaced by the pure resonant harmonies and tones of the room itself.
YouTube has bots that check your videos to make sure you haven't used a copyrighted music track in your video. All these tracks are free to use on YouTube, Facebook, Instagram & Twitch without copyright issues.
This guide shows you how to download tracks from the Audio Library.
There are also lots of sound effects to download too.
Pay special attention to attribution requirements, with any audio user ever.