I think it's a good idea to find a way to integrate songs and instrumentals together. It makes for better musicianship in my view.

One think about Old Time instrumental music. In the culture it comes from, it's dance music. As of late because of the fiddle contests and festivals, it's become isolated from the dance to it's detriment. Without the element of dance it can be very dry and mechanical. A great fiddler makes you want to dance. This is one of the problems with bluegrass.

A great instrumentalist can play backup to a song and take off into an instrumental with lead or backup. The problem is a kind of specialization that you see at sessions. It becomes an exclusive club.

A Doc Watson is a good model. He can do it all with no conflict. There must be many musicians also across the Pond who can do this as well. I love it when the Irish musicians float seamlessly between a go song and go into a tune. American players would do well do emulate this.

What we are going for in our classes is to introduce the idea that one doesn't have to be limited in their abilities to play, sing, play and sing and fit them all together. Exclusivity is a peculiar phenomenom in the interest pattern of Bluegrass, Old Time or some American seisiun players...(I call them Celtoids because they aren't Irish or Scottish, Welsh, Manx or whatever.

From the standpoint of the listener, the non-participant, they would prefer to hear the skilled players or singers in a jam. But this negates the whole idea of what it is...folk music is a social/communal experience. Alan Lomax said that it is the "security blanket" for the sub-culture. Alan Lomax railed against what he considered to be "art song" or European Art Music applied to the performance of folk music. Folk music as show biz misses the whole point. The most important aspect of the music is to bring people in whatever and however possible.

As to song sheets, it's best of people memorize. Sometimes you want to sing a song that isn't memorized. If it's sung enough it will be because the motivation is there to do so. I disagree that a song can't be presented effectively unless it's memorized. Actors read poetry from the page and bring it to life. Singers can do it too but it takes familiarity with the material for this to happen.
Sometimes a crib sheet helps in as a trigger for the first line of a stanza. It the song is a good one, chances are that the rest of the verse follows naturally because it makes sense.

Frank Hamilton