Re: "Fast" keywork
I think there's definitely horns that one would find faster than others.
Speed of keywork comes down to several factors:
1) rods vs screws? Don't know what the advantages would be here. I would *guess* that it depends on wear. Do rods resist wear better than screws? I would think that proper lubrication, condition, and integrity of the rods/screws/barrels/posts would be more important.
2) Key Heights. Horns with lower key height adjusments would be a little faster due to spacial concerns..
3) Ergonomics. If it isn't comfortable for the player to play on, fingering will be slower.
4) Spring tension.
5) Pad condition. If the pads aren't sealing well and it becomes necessary to compensate by placing more force on the stack keys, the speed will certainly suffer.
6) leverage design, especially of bell keys.
7) Noise. while you probably can utilize noisy mechanisms as fast as well silenced ones, there is incentive not to and a player may slow himself down as to try to hide the clunkiness.