Just a suggestion..

according to family legend..

[ I really must do some proper family tree digging..]

My grandad went straight from orphanange to army as a band boy.
I'm guessing the military might have educated him to read music...

If so army service might be a factor in late 19th cent / early 20th cent,
labouring class music education & skills...???

While a soldier, and later as a respected Dunkirk veteran,
my grandad also played popular songs in dance bands and pubs...