TL;DR - I don't believe the advantages of "the blockchain" are relevant to us, and its disadvantages (inefficient, unstable) will only get worse. I think what we're missing is a traditional non-profit.
Firstly, cost: I don't think there is a solution you can build with the blockchain or "smart contracts" which you can't build with ordinary accounting ledgers and traditional legal contracts, more cheaply and with more oversight.
In terms of payment, the transaction fees end up higher than PayPal (once it starts to get congested - see next paragraph). The only advantages are anonymity (does anyone actually freak out that Spotify knows what music you like?) and decentralisation (you don't have to trust a third-party accountant, but you also have no customer service or regulatory body to call if something goes wrong).
Secondly, technology: as a software person with a background in maths and cryptography, I don't believe "the blockchain" is a scalable solution. It is simply too inefficient (proof-of-work is ludicrous, but even proof-of-stake setups have problems) to be able to work effectively once things get big.
The principles behind a blockchain (or directed-acyclic-graph like IOTA, or whatever) have been around and in use for a while - what is new is tying them to a currency system, which people are supposed to invest in for its own sake.
Bitcoin is apparently a success - and certainly, some people have made a ton of money from it as an investment. However, even in the midst of this Stripe stopped accepting Bitcoins as payment, and Microsoft and Steam aren't sure about it either. Recently, a Bitcoin conference stopped letting you buy tickets with it because of speed and transaction fees. Some other currencies look better now, but still they are driven by the idea that the currency is a good investment vehicle.
Thirdly, markets: There is one argument that I agree with: with smart contracts one can design a system that doesn't have a middleman (labels, iTunes, everything) trying to suck up the spare money. People value music and are happy to pay for it, but there isn't a lot of surplus, and too many extra layers makes it not worth it for artists.
Well, you can design a system that allows "direct" payments, but not everyone will be equipped to set up and administrate that, and what then? I think it will end up in the "non-traditional" section of CD Baby's list of outlets, at best.
Labels charge "duplication fees" for digital files, iTunes take 30% (!) because they can (Bandcamp takes 5% for roughly the same service, but still lose out because of convenience and breadth of catalogue - iTunes gets 30% because it's popular enough to demand it.) I think the actual thing we want to disrupt there is... greed, basically.
Creating a technological solution with no middlemen will just grow new middlemen, or existing ones will adapt. Plus, labels aren't completely parasitic and useless. What I think we need is benign middlemen, such as a social enterprise or (even better) a non-profit.