@Appleblossom, I think I recognised about 2-3 of the songs we played. For the most part, I'd listen to the first round or two, then start to join in, simple "one note per bar" first, gradually getting more complex as I got to know it.
It's a very different way of playing compared to Classical music. Classical, you're reading off the score and following your own part carefully. Folk/Celtic, you're listening to the other musicians and playing to complement what you're hearing... while there's a set tune at the base of it, a lot of what goes on around that tune is improvisation.
There was one teenage girl there who was taking lessons from the guy having his birthday. She'd learned one or two tunes off him, but otherwise she joined in playing "single note per bar" spiccato style in time with the music. It was really nice seeing all abilities included, and it got me thinking that this would have been how fiddle and other folk instruments would have been taught in days gone by. Pick up an instrument, join in as you can and learn as you go. 🙂 I was comparing music to language... so if formal music classes are like formal language classes, folk music "education" is probably more like a child learning language by hearing it, starting with "babababa" and moving onto "mum mum" etc.
Continuing the language analogy, I reckon my Classical music education is a good basis, because it's almost the equivalent of knowing a classical language like Latin. Even if you're among people who don't speak Latin, being the basis of so many other languages, it gives a starting point for picking their meaning. An understanding of time signatures, melody and harmony can be applied into any Western musical genre, and a fair few others too.