I've been getting ready for lead in jazz and to get better better endurance I've been using my straight mute. It's been fun trying to play with it since I start using the mute toward the end of my practice session. It takes a while for me to chop out when im not playing loud but the mute gets those muscles working. I encourage all of you to try it now if you have really good range use a harmon now that's some hard work.
Double D and practice