I've primarily seen them used on trombones because traditional lyres suck. They rarely fit the leadpipe and they move around all the time. Bell lyres are much more stable, but that's where the benefits end.

They have a tendency to cause dents in the bell. You are also unable to flip to the other side of the flip folder, so for example if you have 20 stand tunes, you would need 20 sheets instead of using both sides and only needing 10.

Honestly, as a trombonist, I'd rather just hold it with my left hand than try to use either lyre.

I *believe* traditional lyres for other instruments work well enough.