For me the operating principle is this:
The song is the star.
Most of the time transposing rock and pop is not much of an issue unless it creates a situation where, for example, the vocal register goes lower and the bass register has to go higher. That messes with interval separation and can make the song sound cluttered, muddy, or lacking the energy of the original version. I recently had a gig where I had to transpose "Simply Irresistible" to "C". That bass line uses a pedaled "E" a lot. I didn't want want to transpose up gived the aforementioned register conflict so I fired up a 5 string to play it lower. Not being able to nail that open "E" took a lot away from the song. Some tunes are written with a specfic key in mind. Jazz standards - whatever key works. But always, the song should be the star!
The song is the star.
Most of the time transposing rock and pop is not much of an issue unless it creates a situation where, for example, the vocal register goes lower and the bass register has to go higher. That messes with interval separation and can make the song sound cluttered, muddy, or lacking the energy of the original version. I recently had a gig where I had to transpose "Simply Irresistible" to "C". That bass line uses a pedaled "E" a lot. I didn't want want to transpose up gived the aforementioned register conflict so I fired up a 5 string to play it lower. Not being able to nail that open "E" took a lot away from the song. Some tunes are written with a specfic key in mind. Jazz standards - whatever key works. But always, the song should be the star!