There is at least one person who does Amazing Grace with a moving "bass" line underneath. Most people just stick to the key note though, which in my mind is che

There is at least one person who does Amazing Grace with a moving "bass" line underneath. Most people just stick to the key note though, which in my mind is cheating since the whole song is basic pentatonic to begin with. So I definitely agree that the level one might consider a solo song, with melody and changing chord progression and/or oblique harmony, sung by a single person in solo, is rather rare.