Let's just get rid of the idea that we should pay to listen any song. I don't want to have my listening habits quantified or used as a proxy for how much any work of art is worth to me.
We can make this super simple: we can still keep the subscription model, we just need to change the revenue sharing system. Let's just charge a base monthly fee for the streaming service itself (say $1/month) and let's add a monthly "pay what you want" amount where 100% of the value goes specifically to the artists you choose.
So, let's say that I pledge to give $10/month, and I spread that around some 10-15 artists, This means that 90% of the money I am putting into the system is going to the artists. Someone wants to give $20/month, it would mean 95% of the money going to the "right" hands. We wouldn't have to argue about what the "right" hands are because that is defined directly by the people voting with their wallets.