There's a film called Baghdad Cafe (Percy Adlon, 1987) in which a child plays a piano keyboard that makes no sound, being just a two dimensional drawing on a piece of wood. I saw the device used more recently in Honeydipper (John Sayles, 2007). The idea is that as you run your fingers over the 'instrument' you imagine the imagine the sound. It can work as a solitary activity but is not much good for jamming with your mates.
Last night I was playing some new material with Eastern Straynotes in the wonderful 13th century crypt that is Jurnets Bar. The audience usually includes a large proportion of discerning musicians so it feels better than usual when things go well (and correspondingly worse when they go badly). The gig went went reasonably smoothly but in one of the numbers I was still working out the best harmony to put under our guest singer's vocal line. Whereas it had been possible to ad lib in rehearsal to good effect it had relied on being able to hear myself. In a small room, with plenty of reflection off the walls, this was easy. But in a much larger room full of people the lower register on the clarinet was lost in the general fog of frequencies dominated by the bass and accordion. Fortunately, like the silent pianists in the movies, I had a reasonable idea of how the notes would sound against the voice and just hoped any errors were inaudible.
This was by no means my first experience of being unable to hear myself when playing. The anatomy of a clarinet is such that the sound is directed away from the player. My tendency when this happens is to blow harder causing me to overblow and squawk horribly.
In the late 80s I played tenor and soprano saxes in a loud rock band for a time. They had taught me four songs a night for four nights and I'd made notes of the riffs and chord sequences on a piece of paper. The first gig was in a hall in south London and I taped the paper to my microphone stand. My memory of the gig is hazy for reasons I won't go into here but it went down well with the audience and I was very relieved to have got through it. The relief evaporated in Reading, the following night, when I realised I'd left my piece of paper attached to the mic stand. One of the roadies, not understanding its significance, had thrown it away when he folded the stand.
I spent the next year that I spent with the band trying to remember everything I was supposed to do. We never rehearsed again, but the task was made next to impossible by my inability to hear myself play most of the time. The guitarist's Marshall stack was positioned against the back wall each night, just a short distance behind me. No matter how hard I blew there was no way I could compete with that and whenever the sound engineer turned up my microphone to a level where I could hear myself as well the sound from the monitor speaker on the floor would feed back through the system causing that deafening shriek with which you must be all too familiar. And so that was where I learned to play by the position of my fingers alone.
Some nights I could hear myself, as could the audience. Some nights I couldn't be heard at all. But I've no doubt that the worst nights were those on which I could be heard by everyone except me. Any person with half a brain would shut up and mime but I just kept on trying.