I thought I should probably elaborate.
The Ashram and the Academy
Music from The Ashram superficially aligns with Eno's 'ignorable as it is interesting' maxim in sonic terms, but which also seeks 'to induce, evoke or complement certain responses in the listener, 'encouraging states of reverie or receptivity' (Toop), particularly relaxation well being & reverence, through active or background listening. Almost never dissonant, noisy, chaotic or abrupt, generally devoid of tension, drama or narrative, music as an 'empty landscape'. Essentially functional. Douglas McGowan, when asked for a definition says of New Age that 'it boils down to the intention of the artist'... it 'has some sort of utility'. This also fits with the philosophy of New Age and devotional music - the overarching socio-political goal ostensibly being an attempt to bring peace and serenity to society through music whilst also attempting to enhance a personal/spiritual experience.
Examples: Devotional Music, New age, Meditation, Healing tones, Space synths & Planetarium music, 90's chill out, Prog burnouts, Kosmische (the hippie end), Environmental & field recordings, Alpha wave music.
Music from The Academy is ambient music from the classical tradition of performance with an emphasis on experimentation (particularly through technology) and the exploration of new techniques and instrumentation, but which seeks no specific response for the listener. Can be dissonant, noisy, chaotic, abrupt, provocative, dark or dramatic. Generally demands the listener's attention but is essentially non-functional, or at least has no specific function other than to be performed, or to simply be. No grand philosophy other than that of radical modernist impulses to deconstruct and experiment. Austere or mischievous in edifice, degenerate or pious in style, but above all else; serious.
Examples: The Avant Garde - Concrète, Aleatoric Music, Electro-acoustic, Minimalism, Serialism, Tape music, Drone, Experimental electronic, Noise, Post-punk & Industrial experimentalism, Modern classical, Isolationism, Computer music, Glitch, Ambient post rock, Metal drone, 'Power' ambient/manbient.
The important distinction here is in the intended function of the music (or the lack thereof) or the motivation of the artist and the influence this has on the sonic form - not necessarily on the background of the artist in question. So Harold Budd, or Eno, or the likes of Ashra or Tangerine Dream could all be said to have produced work from the Ashram, whereas the likes of Steve Roach, Laaraji, Robert Rich or Ariel Kalma have all put out stuff that arguably fits with the Academy.
When we hit the mid 70's and Eno we see something new. His innovation was not in the form or structure of the music itself, but in the combination of these two traditions. Combining techniques and the experimental approach from the academy with the atmospheric & functional approach of the Ashram, subverting both the performance aspect of the former and the ostensible function of the latter. Eno's ambient 'tint(s) the environment (to) ...modify our moods in almost subliminal ways' (Eno) in a similar fashion to the Ashram, but it does so without the constrictions of the necessity of evoking a sense of well being or relaxation, and can contain dark, dissonant or unsettling elements. 'Music for Airports' is a good example of this fusion - essentially slowed down serialism with loads of reverb, like Aphex's analogue Bubblebaths and their softening of rave and hardcore tropes.
The counter argument there is that Eno simply rebranded New Age (I read an interview with a NA luminary who accused him of this) and there's a fair few quotes from Eno regarding Ambient's 'psychological' benefits to back this up, even parallels between Eno's ambient as 'empty' landscape and Stephen Hill's (Founder of the hearts of space radio show) 'space' (as in mental or contemplative, rather than cosmic) music. Eno is after all a salesman as much as anything else but I think the most convincing rejoinder to this is 'On Land' and its (at times) unsettling and tension filled vignettes, certainly not music to induce bliss or a meditative state. Regardless of the originality of his approach, by creating a definition and coining a genre Eno also created a conceptual space - so you now have these two streams redirected to flow into a lake called ambient - a confluence which creates a huge (and no doubt tranquil) basin where these two core traditions meet and bleed into each other.