I call myself a "musical hedonist" because I don't care "what the composer intended" or a potential listener's experience: Playing piano is for for my own enjoyment alone.
I typically use the word "hedonism" as a charge or accusation, as a contrast to an orientation toward long-term happiness, joy, and prosperity. Hedonism is whim-worship; it's the elevation of short-term desires and pleasure at the expense of one's true interests. There's nothing wrong with pleasure, of course, but when pleasure is pursued carelessly or thoughtlessly, it's ultimately destructive. That's maybe a topic for another post, but the relatively uncontroversial examples of this might be the "recreation" of a drug-addict or the "exploits" of someone who sleeps around in the name of pleasure-seeking, but is really acting out a self-compromising attempt to gain self-esteem.
So when I call myself a "musical hedonist", it's tongue-in-cheek. What I'm getting at is that even though I believe that there are objective standards in art (see here and here from 2014), the value and enjoyment I get from playing piano is just blissfully unrelated to all that.
(Side note: Yes, I realize that the idea of objective standards in art is even more controversial than the idea that there are objective standards in ethics. The arguments are similar, I think, with aesthetics being the narrower application of a similar philosophical approach or set of principles. To get a sense for objectivity in ethics, I highly recommend Tara Smith's Ayn Rand's Normative Ethics: The Virtuous Egoist and Craig Biddle's Loving Life: The Morality of Self-Interest and the Facts That Support It. Only then might I recommend Ayn Rand's The Romantic Manifesto.)
The term originates from an argument I had sometime in 2015-2018 with my brother, Andrew, in which I aggressively and contemptuously told him that "I don't give a shit what the composer intended", referring to things like tempo, dynamics, etc. He challenged me that "what the composer intended" is often a manifestation of well-established conventions and musical language, as well as an understanding (perhaps implicit) of the physiological effects of various musical patterns. He suggested that my doing whatever I wanted when I played, whatever happened to feel good and gratifying, was potentially violative of all that, that it would be "incomprehensible" to an audience.
Acknowledging all that, I think it gets to the crux of my attitude about all this. I just don't care what a potential audience would think or how they would experience it. I'm not playing for them. I'm playing for myself. It's entirely justified by my own enjoyment and mood and whims. I think this is part of why I hate playing for or in front of other people. There's a lot more to be said about that, in terms of "perfectionism" and my muddled feelings about my motives (is it for approval or praise?), but maybe that's for another post.
Interestingly, I don't think that my "hedonism" manifests in a way that would actually be incomprehensible to a listener. It might be different than what they're expecting (based on experience listening to the same piece performed by others), but I think it would still "make sense". But my point is that none of that really matters; what matters is what it means to me.
I think that in the moment, Andrew was still pretty annoyed with me, but I jokingly called myself a "musical hedonist" and now proudly wear that badge to this day. Andrew is pretty serious when it comes to music (and piano in particular--he's a million times the pianist that I am!), both experientially and intellectually, so it was an interesting debate. I think we've gotten to better understanding on the matter since then, though, and a lot has to do with the fact that we're on the same page about the basic aesthetic principles.
Anyway, all that is a big part of why I don't think I'll ever be a piano performer.