Esotery

adapt their subjects to their audience , reserving their esoteries for adepts , and dealing out exoteries only to the vulgar

Source: wiktionary

1839 September 26, "Vindex," Letter to the editor, The Musical World, Number CLXXXIV [New Series no. XCI], Volume XII [New Series Volume V], May 23—December 26 1839, page 334, But a more important division of the musical public, is that of the learned and unlearned, the esoteries and exoteries ; and in no country whatever have I yet heard a perfectly educated musician call Mozart second-rate.

Source: wiktionary

Later on, the doctrine, owing to the contact with the esoteries of the Upanishads, was burdened with scholastic elements: the ideal of an Arhat, aspiring to Nirvana, was excogitated.

Source: wiktionary

1954, William Bruce Cameron, Sociological Notes on the Jam Session, Social Forces, Volume 33, page 179, quoted in 2008, Paul Rinzler, The Contradictions of Jazz, page 54, This means, of course, a continual advance into abstraction and esotery, so that contemporary jazz is always musical casuistry, forever seeking new ways to rationalize the impossible.

Source: wiktionary