Speak of the devil and he shall appear...

As you and everyone at /r/AskHistorians do or should understand, every written document requires source criticism. For a primary source, we need to ask who wrote it, what motivated that person, and how various factors may have affected that person's written words.

In folklore there is an additional problem - as you hint in your question. Not only do we have the same problem that confronts the historian when working with any written document, but we also have a written document that attempts to capture something that was oral - and that spend its life as an oral performance. That adds to the problem that one confronts. To simplify the question, let's first look at folksong.

Lots of things are called folksong, but most popular modern examples are compositions and performances that seem folksy but are really the work of a single artist. Let's set those aside since they are faux folk tradition. The folk ballads (which are sometimes performed by modern folk singers) were captured by a wide variety of collectors of varying capacities and motivations. Robert Burns created his museum of Scottish songs, hoping to preserve dying traditions, but he freely composed lyrics for traditional tunes, added verses to existing songs, or mismatched lyrics with tunes - all as it seemed appropriate. The result is fascinating and even wonderful (who can do without Auld Lang Syne or Scots Wha Hae?), but an enormous amount of source criticism is required of Burns or even of the more reputable Child and his collection of ballads.

When it comes to oral narrative - preserved, recorded variants of folktales and legends, the problem is much the same: source criticism is crucial and not all sources are created equally. The always-cited and ever-famous Brothers Grimm were notorious for abbreviating and censoring the folktales they collected (censoring because many were sexual and excessively violent and suitable for adults only). Many of their nineteenth-century counterparts - or those they inspired - did much the same. Cobbling together the "best of" elements of several folktales into a single telling. And of course, the tendency to abbreviate folktales was practically universal. Those who studied the European folktale in its last waning days before the modern world snuffed out much of the candle found that storytellers often took several nights to tell a single folktale - these were long stories, the folk novels, and like modern novels, they had twists, turns, and considerable detail. Much of this is lost in the standard collections of folktales, so we must be wary when using these sources. The same must be said for Classical sources that captured mythology and other expressions of folk narrative. In these ancient examples, even more caution must be exercised since there is even less of an academic backstop of professional folklore collecting with which to consider the written source.

In general, after the invention of recording devices and the implementation of higher collecting standards, we can view archival examples of folk narrative as being at least true to the word. The Irish Department of Folklore, for example, has hundreds of thousands of pages of meticulously collected pages (and some pages that do meet this standard). Even here, however, we must use some source criticism. Authorities such as James H. Delargy, (Séamus Ó Duilearga: “The Gaelic Story-Teller with some notes on Gaelic Folk-Tales,” The Sir John Rhŷs Lecture, presented November 28, 1945; published 1946) and George Denis Zimmermann (The Irish Storyteller, Dublin: Four Courts Press, 2001) describe a folk narrative tradition that was invariably affected by the presence of a folklorist and his cumbersome machinery. In its original context, the telling of a story or the singing of a ballad was full of life and exhibited in the best of cases the charm and talent of the performer. At the same time, there was often a great deal of audience participation and interaction.

All this means that when we have by way of written documents to capture folk ballads and other forms of folk narrative must be approached the source with caution. At the same time, if this aspect of folk culture is to be approached at all (short of doing one's own collecting with contemporary groups), one must use the written word. It is all we have to understand past forms of folk culture. Like all primary sources, these documents require source criticism. But it is all we have. Wouldn't it be nice to have a 24-hour street cam to witness the comings and goings of a Roman street in the 1st century? Of course. But even there, all we can do is rely on the written word and to understand what documents we have require an evaluation to determine their validity and their flaws.

Does this help? I'm not sure. Ask questions if I can help further.

paging /u/itsallfolklore