I received an email with attachments. The text opened with "Voili-voilou les notes de..." Is voili-voilou known argot for voilà? Or something else?
Yes, it is kind of a jocular alternative for voilà, or voilà voilà !
It is not very used and has no inherent particular meaning, but is definitely understood.
The tone used will tell how to interpret it, but the rare times I heard it, that was to express the happiness to have completed something and to deliver it like "Yeah, here you go!" or to mark that you have finished to tell something like disclosing some story, and soften the end with a "That's all, folks!".