Votre âme est un paysage choisi
Que vont charmant masques et bergamasques
Jouant du luth et dansant et quasi
Tristes sous leurs déguisements fantasques.
Tout en chantant sur le mode mineur
L'amour vainqueur et la vie opportune
Ils n'ont pas l'air de croire à leur bonheur
Et leur chanson se mêle au clair de lune,
Au calme clair de lune triste et beau,
Qui fait rêver les oiseaux dans les arbres
Et sangloter d'extase les jets d'eau,
Les grands jets d'eau sveltes parmi les marbres.
Verlaine's theme here (as often) is that imagination and feeling (the two domains of poetry) are not real. The emotions you get from the poem are only pretend. There is an implication that since the emotions you get from the poem seem real enough, perhaps everything else in life is just as pretend as these are.
The theme is stated just past the mid-point of the poem:
Ils n'ont pas l'air de croire à leur bonheur
Remember that Verlaine was a close friend and collaborator of Rimbaud, whose magical theory of poetry suggested that the world of a poem was more real than the world of either the poet or the reader. Rimbaud's alchemical theory of poetry is a natural transition point between the hermetic mysticism of Nerval's Chimeres and the more explicit angelism of Mallarmé and Valéry.