Emerald green "Performer" mode contains scansion notes.
Before the mid-nineteenth century, virtually all Western drama was written primarily in poetic verse, meaning that the lines had a fixed length and a rhythmic regularity created by patterns of accented and unaccented syllables.
To fully appreciate, and then perform, plays written in verse, modern students and performers need to know how to check the metrical rhythm of the line. This process is known by the very formal term "scansion." It might be much less intimidating if it were widely known by the more contemporary equivalent word, "skimming." It is just a quick perusal to be sure of the intended rhythm.
A century ago it was common practice for editors to indicate their understandings of the spoken rhythm in the printed text. In the '60s and 70s, as fashion began to favor irregular and free verse, this practice fell out of favor in part because so many of these editorial choices provoked controversy. (Of course, there is no reason to impose rhythmic regularity where none exists, but the modern issue is the tendency to fetishize irregularity even when intended regularity is easily discernible.) Avoiding the issue may make the editor less of a target for criticism, but it leaves the actor/reader with no assistance toward learning a fundamental skill. This edition of Midsummer, therefore, assays this task while acknowledging that all scansion choices are ultimately debatable.
This may be less of an issue with this early comedy than with many other plays in the canon because the verse is far more regular than that in later plays. The standard employed for the notes in "Performer" mode is, simply, that the choices which result in the most regular line are the options utilized. Of course, in production, less rigorous conventions might be adopted. Even in those instances, however, it is surely better to make informed choices. In the words of the great Shakespearean director Peter Hall, "The first task in approaching a speech is to make it scan, or find out why it doesn't." (loc. 315).
The good news is that finding this rhythm is much less difficult than it is often made out to be. Armed with just a few principles, and after a little practice, it can generally be accomplished by glancing over the text, and tapping out the rhythm of any tricky lines. The responsibility for giving the lines their metric shape, remember, lies with the playwright. For the user, the responsibility is simply to understand and preserve what the playwright has done.
Scansion can be very contestable, and there is no sense in which the scan offered in this edition (or any other) can be said to be definitive, but "Performer" mode attempts to provide identification of all instances of verse that need a performer's special attention. Words or phrases requiring a decision or an accommodation are indicated with green type. Clicking on the green text will open a note explaining the issue and how to make the words scan regularly. Theses also generally include an indication of current performance practice.
For more information about the principles used in this edition, see the essay, "Practical Scansion" in the end matter of this edition.