Thanks for your response, Jim.

I did not know that backing tracks could be purchased from sites built for this purpose. I will do a search. If you have recommendations, please let me know.

A real example is a Karaoke track for Katy Perrys "The One That Got Away" in the lower key.
https://www.youtube.com/watch?v=9Lm_o0QtU98

I reached out to the channel owner, but did not receive a response.
I would like to have this replicated, or something very close.
In general, we don't need or want melody in the backing tracks. The exception, on a song by song basis, we need to decide how to handle natural solo breaks. We need to either shorten the song by eliminating them, or putting in an actual solo (not preferred), or allow the piano to briefly play the chorus or melody.
I need other POP songs with piano only or guitar only accompaniment similar to this.
For most songs, we should be able to find a karaoke reference or cover reference as inspiration and hopefully eliminate the possibly of something we won't accept.
More often than not it will be in the same key, but will be decided on a case by case basis.
We are far more likely to change the tempo.

The tracks are for vocalists. Paypal or similar.