The typeface of early modern plays tended to differ when prologues, epilogues, songs, and letters were printed. Prologues, Epilogues, songs, and letters are also often distinguished by titles that set them off from the rest of the text, despite these being generally textually apparent (113-114).
It is not uncommon for early modern texts to simply describe where a song should go, such as in Julius Caesar [4.3], where Lucius plays a song for Brutus (115). This also occurs in Pericles [Q H3b 5.1] and 1 Henry IV [3.1] (116).
When printed in early modern texts, it is not uncommon to find songs printed as appendixes to the plays. This is probably because songs would have been kept separate from the play book, and thus would have been printed separately, or perhaps not at all. It is possible they were kept separate for use by the actors; actors could take the song (accompanied by its music) with them on stage to sing (117).
Prologues, like songs, were also fluid. All's Lost by Lust, and Wonder of a Kingdom, two plays separated by three years and two different authors, have the same prologue. Where several of Shakespeare's plays that do not have prologues speak of prologues as being common components of a play text, Richard III has a prologue written by Heywood for a Queen Anne's Men's boy player (118-119).
"Prologues and epilogues were not part of a unified text, sharing the same rights and lasting qualities" (120).
Prologues and epilogues may have been written for specific, one off court performances, which would have a different flavor than their counterparts for public performance. Surviving prologues for public performances tend to share common themes of at once asking the indulgence of the audience and inviting them to judge it, and
epilogues tend to directly ask their audiences for applause (120-121). These prologues and epilogues were essential features of an opening night performance, but if the play 'passed' its opening night test, would be subsequently dropped from future productions (122).
The character of the prologue appears to have been dressed in a black robe and hold a garland, the symbols of the scholar and the poet. An actor in the company thus plays the role of the author, and by extension transfers the authority of the play to the company (122).
"A play in performance was by no means textually fixed" (122).
Textual instability was a key feature of any part of an early modern play text. Songs, prologues, epilogues, and letters would generally not be included with the printed text because they were different pieces of paper from the play book. Likewise, plays were written in parts, and playwrights could take advantage of the custom of parts and cues to create scripted gibberish that would have been apparent in performance, although not necessarily in the company book. The texts of the plays, designed to be performed, were inherently mutable, and thus the texts that we know should not be considered as fixed entities of singular poetic genius.