Yep! Songs I have sung for more than forty years began to lose a bit of something. Eventually, I realized that the high and low of my optimal vocal range had changed. It was time to change keys to accommodate the range. In my case, I have lost a bit of my upper range, defeating the possibility of simply capoing. Transposing to a more suitable key has been a slow process in the doing. After all, one gets pretty used to playing a song in a particular key and the sounds each chord produces. This is especially true for me because I can't always fingerpick the melodies using the new chords.

Congrats on your discovery and especially upon the effect.