What's the difference to MUSICONOMI?
Let me quote this.
Voise, Musiccoin and any other similar "coin" is basically bitcoin but with a diff. name, These tokens/coins are only used on their respective websites while Opus is an entire music sharing infrastructure. We store songs and all metadata data in a decentralized and rapid IPFS swarm and Ethereum.
API's for third party player developers are also soon be released for them to help create their own Opus players.
Opus even has a working beta and a demonstrable product, unlike some of these past music oriented projects. Going on ICO's without even a hard product to show off.