OpenGameArt.org
Waltzing Matilda
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"Waltzing Matilda" by FiveBrosStopMosYT licensed CC-BY-SA 4.0: https://opengameart.org/content/waltzing-matilda Author's attribution notice: Waltzing_Matilda by CambridgeBayWeather, is licensed CC-by-Sa-3.0/4.0.
Where to put it: Game credits or video description. If the entry has a "Copyright/Attribution Notice", follow that.