It gets even more complex if you take the fairness he's suggesting to it's logical conclusion. The system proposed still values playing each song equally, but shorter songs comprise less of a user's streaming activity.
So the per play rate should be determined by taking 70% of the user's subscription, dividing that by the number of seconds of streaming that user streamed that month and then multiplying that by the number of seconds that user streamed the artist's song (since songs can be stopped mid-song).
Regardless of how they bill, it's likely that artists will have to, for the most part, just trust Spotify. There can, and should, be independent audits of the billing code. It seems an analogous situation to what the NGC does around computerized gaming systems. Users have to trust that the system is fair, but the NGC is very thorough about checking that code complies with applicable laws.
So the per play rate should be determined by taking 70% of the user's subscription, dividing that by the number of seconds of streaming that user streamed that month and then multiplying that by the number of seconds that user streamed the artist's song (since songs can be stopped mid-song).
Regardless of how they bill, it's likely that artists will have to, for the most part, just trust Spotify. There can, and should, be independent audits of the billing code. It seems an analogous situation to what the NGC does around computerized gaming systems. Users have to trust that the system is fair, but the NGC is very thorough about checking that code complies with applicable laws.