I like drones. They play the correct note, which I may or may do. I have a drone CD which I bought from http://www.navarrorivermusic.com/cello_drones.php for about $10. Then I entered the 21st century and found a Tuning Drones app. It works too. Anyway, I have an arpeggio in a piece that goes G-B♭-C♯-E♭ (on the G string); G-B♭ (on the D string); C♯-E♭-G-B♭-C♯-E♭-G (up the A string). Not so hard, right? Only for me it was. I started by playing it bow-only. When I have trouble it’s often my right hand that’s the problem and if I leave the left hand out of the training, my right hand will learn what is needed. After right hand training, I use the drone, but which note to drone? Easy answer. All of them, one at a time, and repeat. It really helps. Then play the arpeggio backwards. High G-E♭-C♯-B♭-G etc. With the drones, of course. And repeat. And this was the only thing from this piece I practiced yesterday. Sometimes focus on a very small thing improves in many ways.