It is unknown who sang the early 70’s 2NX version of the 2SM network jingles. They were more end of break jingles rather than between songs. The NX call sign was a pain because if you dropped the music in too tight the X was cut off in the mix. Most of the jingles came out as 2N-ek. The X’sss was lost because of the action of the excessive compression / limiter settings common for AM radio.
thanks again to Michael Dalton, for this info