The 'reconstructive movement' was concerned with the recreation of Elizabethan acting conditions, and would eventually lead to the creation of Shakespeare's Globe and similar replicas. One of the movement's offshoots was in the reconstruction of Elizabethan pronunciation: for example Bernard Miles' 1951 Macbeth, for which linguists from University College London were employed to create a transcript of the play in Elizabethan English, then an audio recording of that transcription, from which the actors, in turn, learned their lines.
The pronunciation of many words evolves over time. In Shakespeare's day, for example, "heath" was pronounced as "heth" ("or a slightly elongated 'e' as in the modern 'get'"), so it rhymed with "Macbeth" in the sentences by the Witches at the beginning of the play:
Second Witch: Upon the heath. Third Witch: There to meet with Macbeth.
A scholar of antique pronunciation writes, "Heath would have made a close (if not exact) rhyme with the "-eth" of Macbeth, which was pronounced with a short 'i' as in 'it'."
In the theater programme notes, "much was made of how OP [Original Pronunciation] performance reintroduces lost rhymes such as the final couplet: 'So thanks to all at once, and each to one, / Whom we invite to see us crowned at Scone'" (5.11.40-1) where 'one' sounds like 'own'. The Witches, the play's great purveyors of rhyme, benefited most in this regard. So, 'babe' (4.1.30) sounded like 'bab' and rhymed with 'drab' (4.1.31)..."
Eoin Price wrote, "I found the OP rendition of Banquo's brilliant question 'Or have we eaten on the insane root / That takes the raison prisoner?' unduly amusing"; and he adds,
:... 'fear' had two pronunciations: the standard modern pronunciation being one, and 'fair' being the other. Mostly, the actors seemed to pronounce it in a way which accords with the modern standard, but during one speech, Macbeth said 'fair'. This seems especially significant in a play determined to complicate the relationship between 'fair' and 'foul'. I wonder, then, if the punning could be extended throughout the production. Would Banquo's lines, 'Good sir, why do you start and seem to fear / Things that do sound so fair?' (1.3.49-50) be fascinatingly illuminated, or merely muddled, by this punning? Perhaps this is a possibility the cast already experimented with and chose to discard, but, for sure, an awareness of the possibility of a 'fair/fear' pun can have interesting ramifications for the play.