General Recommendations for cleaning your piano during the COVID-19 period:
Use alcohol-based disinfectants, do not use bleach-based disinfectants or any product containing citrus.
If using a spray or liquid bottle, use a disposable towel like WYPALL L30. Put the disinfectant on the towel and not the piano.
After use, immediately put the towel or disinfectant hand wipe in the trash and wash your hands as the CDC recommends. Do not use reusable towels or cloths which could spread germs.
Always follow up with a dry towel and never leave any liquids on the piano or keys.
Keys
The keys are the most important part. Generally speaking, most disinfecting wipes or sprays should be safe to use on the keys. If the keys are dirty, I suggest using Cory Key-Brite to clean and then follow up with the disinfecting wipes or sprays.
Case Parts
Always test the disinfectant in a discrete area before moving forward to ensure there is no adverse reaction. Check to make sure the finish does not come off on the wipe or towel, the finish discolors or changes sheen. If none of this happens after a few minutes, you should be able to proceed.
High gloss polyester is the most durable to almost any store-bought disinfectants. Always do the test first. If the finish is dirty, use Cory Pre-Polish Finish Cleaner, followed by the disinfectant, then for the final step use the Cory Super High-Gloss Piano Polish. Make sure to always follow up with a dry towel.
Polyurethane and lacquer finishes require a more careful approach. Disinfectant wipes and sprays may be harmful to these finishes. Test an area first. In these cases, I recommend a few drops of hand/dish soap with warm water on a towel. Make sure to always follow up with a dry towel.
For satin pianos always wipe down the piano in the direction of the 'hand rubbed' finish or grain. Going in the opposite direction may result in hazing or scratch marks.
Aged, alligatored, and damaged finishes are a challenge. It is difficult to know what is best to keep the integrity of the finish and still clean thoroughly. Always test an area and proceed with caution.
Cleaning pianos is a gentle process not a scrubbing process. Pressing hard or vigorous scrubbing may lead to scratching or removing the finish. Always proceed with caution and use common sense. Remember to wash your hands after you have thrown away the towels or wipes. perform best under consistent conditions neither too wet nor dry, optimally at a relative humidty of 42%.