Being on hold is the ultimate liminal space.
First, the "best". It's Tim Carleton's Opus 1, automatically downgraded into its own Amiga MOD version by the Texas DMV. You've almost certainly heard it because it's the default in Cisco Systems' office VoIP setups.
Now the "worst", an … AI trained on Autechre and filled with hate? I've experienced this one myself, but this recording was made by Vic Berger.