With most Hongkongers staying home to help stop the spread of the deadly coronavirus, Ming’s Piano lost 70 per cent of its normal operating profit during its worst month in February since the outbreak started in the city. But the music instruction centre recently managed to get some students in front of carefully sterilised keyboards in mobile classrooms made by loading pianos onto special trucks. The centre’s first “piano truck” hit the road on February 20, 2020, and since then two others…