Yes, by "band asking the bar to play for free (i.e. the producer going to the advertiser)" I mean the band are the producers of the product, and the band are initiating a transaction with the bar who are the advertiser for that product. The only time I'd expect the transaction to be initiated the other way around, i.e. the bar going to the band, would be when the power dynamic was inverted, e.g. it was a less well known bar asking a more famous band to play there to try to attract custom to the bar, but in that case I would expect the band to be asking for payment not offering to play for free, and in doing so they would effectively switch roles, i.e. the band would take on something of an advertiser's role and the bar becomes more like the product that is being advertised, in which case I think the original point about it normally being the producers of a product initiating transactions with the advertisers of the product rather than the other way around would remain.