Purely playing devil's advocate here - Keep reading that definition you pulled up!
"There are many different definitions of productivity (including those that are not defined as ratios of output to input) and the choice among them depends on the purpose of the productivity measurement and/or data availability."
So really what we're arguing about is the "purpose of the productivity measurement". I don't think "number of melodies that will never be listened to" is a particularly good measure for "DJ", but it is a great measure for a blog title.
"Productivity is the efficiency of production of goods or services expressed by some measure."
An whole album with millions of melodies in just one morning is quite efficient :). Meaningful or deep, maybe not. But productive... yes!