I have long been on the lookout for something to replace work on scales, which. though necessary, can sometimes make one forget the main object: developing portamento, opening and broadening the sound so that the player's expression is both relaxed and natural. I was therefore delighted to find these 'ferma' or rather cadenzas by M.F. Hofmeister.
Rather than working at them in the order in which they are presented, it is I think better to pick and choose. As I personally very much like the keys of F and C, I often start by playing the 'ferma' in these keys, ending with those in D.
If some of these cadenzas seem especially pleasant to work at, do not hesitate to transpose them, and you could then improvise new ones.