Back in the seventies, when I was first looking into the possibility of focusing on a music career involving pro-quality performances on the piano, there were very few options available to piano players who wanted to be able to rock out and be heard by the kind of audiences common at that time. Regular microphones tended to cause significant problems with feedback, which could be painful to hear if one was an audience member. But people were working on the problem. There was the Barcus-Berry piano pickup, and there was the Helpinstill, which was used back in the day by musical artists like Leon Russell.
Amazingly, there is still an active web site for Helpinstill. I was interested enough in the Helpinstill that I took a trip from College of the Ozarks to the Six Flags amusement park near St. Louis, just to see what benefits it might have to offer. They kindly let me try out their piano there, and I was amazed to hear the sound of a grand piano coming at rock music volume levels from the P.A. system.
These days, that's not so amazing, and there are digital pianos which manage to capture the sound of grand pianos, with significant advantages in terms of speed of setting up, and of course, in terms of such issues as tuning. (The Roland V-Piano Grand is my current favorite.)
Still, the Helpinstill pickup was quite a boon for people who were tired of being limited to the Rhodes, the Wurlitzer and other electric pianos which sound very little like real pianos.