You may not know that Justin Morgan's primary profession was actually singing teacher, one of those location- and era-specific professions that baffle us today.
He also composed a number of songs, one of which is still somewhat famous today, AND was named after me.
(obviously not really but I'm still going to claim it)
Here's a gorgeous symphonic interpretation of that same basic melody by composer Thomas Canning.
So, if you've read Marguerite Henry's Justin Morgan Had a Horse and like me hold dear the image of a lanky and laconic New Englander striding his way through the wilderness, followed by a scrubby colt: this is the music that was in his head.