Act Two may be seen as the conflict of a rock star versus his critics, originally discussed in the Chateau sessions as 'Only Solitaire'. Note that 'Nightcap' allows us to see how the 'Critique Oblique' section was intended to fit into the aborted Chateau double album - directly following 'Only Solitaire'.
The Play's 'Actor of the low-high Q' may be considered a representation of Ian himself (see the main interpretation, but apply my comments to Ian rather than Ronnie) - he's very clearly an intelligent individual, prepared to act the low-brow clown and prance about in a codpiece. This also applied to Jeffrey H-H, who hid a shy, even reclusive personality behind a grandiose stage persona.
Ian's 1974 interviews (e.g. Melody Maker 7 Dec. 74) show him to have been struggling to resolve this perception of himself, mainly to counter the charge that his stage 'self' was false, merely an act, a set of crowd-pleasing antics repeated ad infinitum for the sake of applause ('Only Solitaire': "And every night his act's the same")
the low-high Q
may be a development of 'Only Solitaire's:
His oratory prowess,
his lame-brain antics and his jumping in the air
The concept of 'the dressing room' in APP actually fits much better into the imagery of the Chateau material, both as a metaphor and as part of the (rather loose) narrative.
Ian expands the idea a few lines later in Act 2, discussing his relationship to the critics via his position as a stage-performer. As Andy says:
"In the lines:
Man of passion rise again, we won't cross you out:
for we do love you like a son, of that there's no doubt.
The 'we' may represent the music critics (Steve Peacock in particular it seems) who with a few words can crucify a performance (hence the more mundane meaning of 'cross out', with a pen or pencil -- delete, edit, etc.). Here, the critics are rather superciliously assuring him that he'll get good reviews, and that they really do 'love' his act. This is just hot air, of course:
Tell us: is it you who are here for our good cheer?
Or are we here for the glory, for the story, for the gory satisfaction
of telling you how absolutely awful you really are?
This is the same unified voice of the critics in 'Only Solitaire' - "tell us"... "bless us all". They like nothing better than to point out how bad the act is in as many choice words as they can muster."
This sheds new light on earlier lines in this scene:
Lover of the black and white* it's your first night.
The Passion Play gets in the way, it spoils your insight.
*('Critic of the black and white' in the Chateau version of 'Critique Oblique')
Might suggest that press critics ('black and white' implying newspapers), new to his music ('first night') mightn't understand his music & lyrics. Professional music critics, hearing similar music night after night, having heard other, ostensibly similar music (Well... all 'art-rock' is the same, innit?) and already being aware of Tull's reputation, are bound to carry preconceptions, colouring their perception of Tull's performance.