Act I of The Importance of Being Earnest begins with Algernon Moncrieff playing his piano, whether "accurately" or not, while his manservant, Lane, enters the scene.
While the two men only engage in dialogue in Act I, and this is not an extensive dialogue, a lot can be inferred from the level of tolerance that both men display toward each other, even when the things they talk about are on the harsh side, maybe even demeaning from one part to another.
The men's discussion of topic of marriage, one of Wilde's favorite points of mockery, stems from a discussion about champagne. The idea behind juxtaposing champagne to marriage is to bring out the irony behind courtship: the feeling of ecstasy caused by the drunkenness of love is as ephemeral as the drunkenness caused by alcohol. Hence, the question is: is love a real feeling or a passing emotion?
Lane. I attribute it to the superior quality of the wine, sir. I have often observed that in married households the champagne is rarely of a first-rate brand.
Algernon. Good heavens! Is marriage so demoralising as that?
Back to the relationship between Lane and Algy, notice the flat affect in the conversation between the two. Even when the men seem to agree in most of the things that they discuss, it is clear that the men do not match. Lane is older and middle class while Algy is fashionable, young, and wild. This is an uncommon practice among upper class Victorians, who would want a servant to match and serve as their shadow; someone who would know their tastes, and indulge their whims.
However, it is clear that Algernon lived above his means. He did not have "ready money", had lots of creditors, ran high bills, and tended to run out of town whenever responsibilities reached him. The conclusion out of all this is simple: Lane is the only manservant Algernon could afford. The fact that the men were unfit for each other makes their flat relationship make sense. Algernon did not care for Lane any more than Lane cared for Algernon.
Algernon. [Languidly.] I don’t know that I am much interested in your family life, Lane.
Lane. No, sir; it is not a very interesting subject. I never think of it myself.
Algernon. Very natural, I am sure. That will do, Lane, thank you.
Another role that Lane fulfills is that of an accomplice. Lane is obviously so attuned to Algy that he finishes the lies that Algernon starts. He easily follows along Algernon's lie about the cucumber sandwiches that were intended for Lady Bracknell, but that Algernon ate himself. Lane is also aware of Algernon's Bumburying and even knows the wardrobe that Algernon prefers to use when he goes about town leading his double life.
Hence, it is clear that, although the men are awkwardly matched in terms of age, lifestyle, and experience, Lane neither condones nor condemns Algy's comments or behaviors regardless how demeaning or amoral they are. The men may very well be interdependent on each other: while Algernon provides Lane a home and a salary, the latter in turn provides a non-listening ear and an quick alibi for whatever trouble Algernon gets into. It is the perfect match for Algernon's lifestyle, at least.