Song snatches in Old Time tune sessions

During the late night Old Time instrumental sessions at the Sore Fingers music camp I’ve noticed small song snatches were sometimes sung at the beginning of a tune. Maybe this was just for fun but I assume it also functioned as a way to convey the tune more easily to other players and that maybe these snatches were used as an aide memoir during the learning process.

As it is generally accepted that vocal melodies are easier to absorb than just tunes, I was wondering if there are any collections of these snatches for popular OT tunes. I appreciate, of course, that many fiddle tunes also function as songs with full lyrics, but for this purpose single verses would suffice.

I mentioned this to a friend of mine who regularly participates in Old Time sessions all over the UK, but he had never encountered it...

There are some interchangeable lyrics that show up in different tunes. I think some of the June Apple lyrics can be sung in other tunes as well as other song/tunes.

That's true of songs too. I believe they are called floating verses.

I've thrown a sung verse into appropriate fiddle tunes at various jam sessions, but not used it at the beginning to "establish" the tune or its melody.

E.g., the 27th time through Soldier's Joy I may borrow the Skillet Lickers'

Rock the cradle, Lucy, rock the cradle by,
Rock the cradle, Lucy, don't let the baby die

Always good to avoid infant death at an old-time session.