As this thread tails off the spool, I the thread-starter (I don't know what OP stands for) should express my thanks and make some remarks.

I appreciate the thought and even erudition that went into posts to the thread, especially given the imprecision in my laying out of the subject.

In speaking to points well taken, this post may seem a bit disjointed.

It is true that we often call "songs" musical pieces that were, to our knowledge, never sung. I believe that I henceforth may tend toward "melody" as the term for such a piece.

I accept that the use of ornament, in instrumental and vocal lines, was quite important in many times and places. Convention, gratuitousness, oneupsmanship, and instrument characteristics aside, I haven't begun to find out what particular ornaments signified; I presume there were signified meanings for some of them.

The traveling and court minstrels of various types must have been amazing, not only for their instrumental accompaniments and perhaps solos, but for their use of verse forms, sometimes extemporaneously, before very critical audiences. When we marvel at the lyrical output of a Bob Dylan, for instance, perhaps we should reflect on what has changed in our expectations, in that he would stand out even without attempting mastery of verse forms.

"Fills" I should have precisely defined as to what I meant; there might be a better term. No harm was done, though, for all of the discussed instrumental interludes, short or long, pertain to how a song is served by the presenters and received by the audience.

Granted, the songwriter who composes and performs a song on an instrument may consider some or all instrumental components to be part and parcel of the song.

I tend to think of songs that can be sung a cappella, without long gaps, as standalone songs. I tend to think of songs with long rests within the verse and/or refrain structure, to be filled with instrument playing, as fills-dependent songs. I have become a bit partial to the standalone kind, although many of the fills-dependent kind I consider fine, artistic songs.

I must hand it to some of the modern string bands and jazz bands. They can take a standalone song, create introductions, endings, fills, and solos comprising improvised variations, without doing disservice to the song. We should not forsake simple delivery of standalone songs, however, even if we expect to never be marooned, quarantined, or imprisoned.

I should begin a list of the two kinds, by my lights, whether they be "folk" songs or not, for contrast. For example, "Auld Lang Syne" (sp?) might be performed a cappella or with singing and instruments. If you perform "Knockin' on Heaven's Door," on the other hand, you'd better have your strumming or picking chops ready.