I don't know... chant musics
                are frequently intended to bring on a trance in the
                listener. Chants are used in the ritualistic events that
                underpin certain cultures, traditions, religions, etc.
                
                I've been brought to places while in a deep focus (aided
                by chant musics) that parallel experiences I've had on
                psychoactive drugs.
                
                In that sense, Eno's description is sort of perfect to
                me. Gregorian chant was used to induce religious focus,
                so the music itself does sort of fall out of primary
                consideration when "used" correctly.
              
          
          
            Eno absolutely meant "ignorable" in
              the normal dictionary way. He did not mean
              "trance-inducing", or "religiously focused". Eno's coinage
              had absolutely nothing to with "inducing" anything.
            
            
            -------
            
            Eno remembers the event somewhat
              differently. “After she had gone, and with considerable
              difficulty, I put on the record,” he recalls. “After I had
              lain down, I realised that the amplifier was set at an
              extremely low level, and that one channel of the stereo
              had failed completely. Since I hadn’t the energy to get up
              and improve matters, the record played on almost
              inaudibly. This presented what was for me a new way of
              hearing music – as part of the ambience of the environment
              just as the colour of the light and sound of the rain were
              parts of the ambience.” 
            
            
            
            [ ... ]
            
            
            All this sounds like a recipe for
              boredom, and for many people that’s exactly the result
              when they listen to Music for Airports. For others, the
              fact that the music is so quiet and so content to
              circulate such thin little scraps is the secret of its
              appeal. Eno himself describes the album as being “as
              ignorable as it is interesting”. 
            
            
            
            
            [ and may the universe not react to
              harshly to me citing the Daily Telegraph ]