Erik Satie, Gymnopédie no. 1, arranged for harp. Performer credited as "Anonymous" on Musopen.
No attribution is required and there are no use restrictions. This was chosen deliberately: the three straight-piano Gymnopédie recordings on the same Musopen page are CC BY-NC-SA, whose ShareAlike term would arguably propagate to the published episode, and the only Pachelbel Canon recording there is CC BY-NC-ND, whose NoDerivatives term forbids using it as a bed at all. Verify the license badge before ever swapping this file.
The composition is public domain (Satie, 1888), but that is not what makes this usable — the recording carries its own copyright, and this particular one is marked PD. Musopen's forum has open threads about YouTube Content-ID claims against this very recording; podcast distribution isn't scanned that way, but the provenance above is recorded here in case a claim ever needs answering.