Opus is interesting, especially with the progress they've made on the IPFS approach to music storage (which is actually how the Musicoin.org platform handles it too). But since it is a entirely ETH-based they aren't using the same Pay-per-play micro-transaction schema as the underlying Musicoin technology, purely due to prohibitive transaction costs in eth, you have to buy the track outright. So it's basically chinese iTunes on blockchain. They have their own challenges, and I wish the team luck. Innovation and competition is healthy for all parties involved.

Right now the smart contract charges one mc per play, but we intend to switch that up to allow artists to set up the smart contracts on a per-track basis to allow them to charge however much they think is fair for a play, including fractions of a musicoin.