In 1473, a London bookseller named William Caxton collaborated with a Flemish printer named Colard Mansion on a project which would bring overwhelming changes to English culture: The Recuyell of the Historyes of Troye, Caxton's own translation of a Burgundian account of the Trojan War. It was the first book ever printed in the English language, and Caxton sold enough copies that he proceeded to invest in setting up his own press in Westminster - the first in Great Britain. In 1476, he released the first title from his Westminster press: a mass-produced edition of the Canterbury Tales (which draws on enough folkloric material I guarantee I'm going to write a post or two on it later).
Caxton would go on to print 87 known titles, 26 of which were his own translations of foreign materials. While his aims were much the same as any modern translator's - accurately presenting the foreign material to English readers - he doesn't seem to have been very good at it, and a great many foreign words show up in his translations. ("Recuyell," for example, is not and hasn't ever been an English word, and I would never be able to read his 1481 History of Reynard the Fox without modern footnotes explaining the Dutch words therein.) Still, business was good, and by the 1480s, other printers had begun to operate their own presses in competition with Caxton. Caxton responded by expanding his shop through the help of his business partner, Wynkyn de Worde, who would go on to take over the business after Caxton's death in 1492. By the 1500s, there were a great many of them, and the publishing industry ballooned. Soon, printed material was a part of everyday life for the middle classes.
One of the products of this explosion was a sharp upswing in the composition and spread of ballads.
Defining a "ballad" is a bit difficult, but it is a form of popular poetry that is usually narrative, frequently in what we now know as "common" or "ballad" meter, typically anonymous, and usually intended to be sung. Nowadays they're often part of the oral tradition (though many traditional Appalachian singers use the term to refer to any song they learned from a written source), and they often originate with oral transmission as many folk songs do, but during their heyday (about 1550-1850) they were most often distributed in printed form. The printed versions, most often the work of a single editor if not truly a single author, incorporate what is well-loved in the oral tradition.
Ballad subjects varied wildly, from accounts of great historical battles or fights against pirates on the high seas, to love songs, to tales of Robin Hood (these last having some of the strongest ties to the oral tradition of any early ballads, and printed primarily in the 16th century).
The most typical form of printed ballad was the "broadsheet" or "broadside" (some experts distinguish the two, with "broadside" referring specifically to those printed on only one side of the paper), a large-format (often folio-sized) piece of paper with the words of the ballad and an instruction as to what well-known tune it was to be sung to printed on it. (Some give an indication such as "to a pleasant new tune," but the tune is almost never provided in written form.) Until the late 17th century, these were commonly printed in blackletter type and decorated with a woodcut (usually a stock image at most tangentially related to the actual content of the ballad); this format was gradually replaced by roman type without images. Broadsheets were sold by street vendors who sang the contents (thus ensuring oral transmission of the melody and advertising the quality of the song to anyone who wished to buy the words and actually learn them properly), and many were pasted on the walls of pubs to facilitate group singing. By about 1600, ballads were everywhere, and would not start to decline until the end of the seventeenth century. Even then, the decline was gradual; in fact, broadsheet printing was still vibrant into the 19th century. These printings provide a record of the popular music of three centuries before a rise in musical literacy led to alternate forms of music publishing coming to prominence.
A great boon to modern folklore and ballad studies, and to the coffers of the printers, was the grant in 1557 of a royal charter to the Worshipful Company of Stationers, which authorized them to seek out and destroy any printed material not produced under the aegis of their guild. The Stationers had a policy of requiring registration of printed works, and forbade the printing of anything not entered into their registry. Registration also gave the printer who registered it the exclusive right to print that work, like an early form of copyright. Unlike modern copyrights (which first began in 1710 with the Statute of Anne) there was no requirement that the registrant be the author of the work - in fact, several of Shakespeare's plays were registered, likely on his behalf, by members of the Stationers' Company, as non-members did not have the authority to register a work. Nor was there any kind of prohibition on the creation of derivative works; new variants of old ballads commonly show up in the registry as belonging to printers unconnected to the ones who held a patent on the earlier form. This feature served to encourage innovation within any given text, as a best-seller would quickly spawn attempts to publish a version even more strongly to the public's taste; naturally, it did a very poor job of rewarding the original poet when their work was overtaken in popularity by a knock-off. This was not seen as a problem; Stationers' Company registration existed to benefit publishers, and any advantage it offered to authors as well was a happy accident.
In practice, however, registration was treated as optional. About half of all surviving broadsheets from the 1557-1710 period are unregistered, and presumably the same proportion holds for those which no copy of survives. Nonetheless, registration dates are quite helpful in tracking the history of the ballad form throughout that period.
Today, thanks to the modern wonders of the internet and flatbed scanners, a wealth of old ballads are available to us once more; the good folks at the University of California at Santa Barbara's English department have created the English Broadside Ballad Archive, which offers free access to a searchable database of over six thousand broadsheets with facsimile images and full-text transcriptions. For many, the tunes are known, or at least intelligently guessed at, thanks in part to their preservation to the present day in the oral tradition and in part to the efforts of Ravenscroft, Playford, D'Urfey, and other compilers of popular melodies from the seventeenth and eighteenth centuries; in many cases where the tunes are available, EBBA provides a recording.
It should be noted, by the way, that the printing press did not invent the ballad. Indeed, one of the oldest ballads known, "Judas" (Child 23), is first attested in 1330, and the text is believed to have been composed several decades prior. However, while the ballad form certainly existed in the fourteenth and fifteenth centuries, it only began to pick up so much steam with the growth of print as a method of propagating song and poetry.
While a great many ballads have been lost, many have survived in the oral tradition, in greatly changed form. For example, the oldest version of "Riddles Wisely Expounded" (Child 1) is a Middle English text under the title "Inter Diabolus et Virgo" - but a modern descendant remains current in Appalachia as "The Devil's Nine Questions." Compare also the modern Scottish folksong "Captain Ward" with the seventeenth-century "The Famous Sea-fight between Captain Ward and the Rainbow" (Child 287). The broadsheets record the greatest pop hits of their era, and the better ones are still recognizable as classics, so that many are not forgotten even today.