Oh, that is so not a joyful noise!
It sounds like a wireless doorbell, or similar. It seems to have an analog character and a tonality that says an alert chime of some kind.
Tough to say what the source was. Someone from the venue might recognize it. Like the "order's up!" tone in the kitchen, etc. It sorta sounds a lot like the tone you hear in some places when a door is opened. Maybe a wireless version.
So the question is, how did it leak into all channels of your recording. Did it come in via a cable issue, or some other path. If it was a cable issue, you'd think it would be confined to those channels.