I live in a desert climate & must run humidifiers 24/7 to keep my harps at 50%. My solution, after quite a few arrangements, is set at 3, 1gal. Humidifiers. They each have a high/low setting so depending on the day’s humidity, they are set at different speeds. During the winter w the heat on, I had to run all 3 on high. Right now, I’m doing 1 high, 2 low but I check each day & make adjustments. My dream is a climate controlled room for my harps!
I got mine through Amazon, Bell & Howell ultrasonic humidifier. It works great! Even changes colors if you want. It’s quiet and lets out a fine mist. You can adjust the level.It was not very expensive either.