I bought a digital piano with a fixed height stand and the top of the key are 28.75 inches from the ground. I need to get my elbow to be parallel with the key height, is what I got from online videos. So either I get an adjustable stand and set it at a lower height or get an adjustable chair and set it at a greater height (and be sort of standing). I've been using a dining room chair and my thigh is parallel when I sit on that chair. My elbows are about 25 inches from the ground when seated. I'm not sure what's the best approach.
- Adjustable stand
- Adjustable chair/bench
- Sit forward on the chair, so your feet can be flat on the floor
In my experience, #3 is the most common issue, and the easiest and cheapest to fix. Pianists should sit as close to the front edge of the chair/bench as is comfortable. This allows for weight in our feet on the floor or footrest, which supports our back. It also makes it easier to move when we need to play in the high or low registers of the instrument.
The two factors that are important are elbow height compared to keyboard level, but also feet on the floor. Let's be stupid: you could raise yourself and the keyboard another 6", and the arms wouldn't change. But your feet would be dangling!
So, let's start where the floor is.Heels resting on it, so you can work the pedal/s comfortably. Sitting (not slouched) will give you the elbow height, so then the keyboard height can be adjusted. I prefer elbows sligtly higher than the 'board, so gravity will help lower arms/wrists/hands when needed - most of the time.