I proposed to publish some ideas on my blog (see my original post Inventions). These are ideas which I think might be viable, which I don't have the time to dwell on myself. I have done a few designs with electromagnets, and have felt in my hands the repulsive "pressures" of electromagnet and magnet combined. Now consider that musical keyboards today have touch-sensitive keys. These at first were simple switches. Now they are quite sophisticated. Yet one thing seems to me to be always the same: key pressure -- which is, the pressure which is required to depress a key. This could be varied, through the use of electromagnets (and possibly other means). Not only could one vary the pressure of all keys, but of keys individually -- and not only of keys individually, but one could vary pressure through that brief moment in which a key is pressed. I cannot predict exactly what this would do, but I think it would noticeably change music. It could, too, simulate old keyboards. OBSERVATION: Perhaps it has been invented before, but I do not find it.