Dear Sir,
You are certainly on the right lines with Beckmesser. But don’t overdo the man’s foolishness; it will take care of itself: he does not need to be old; many people are already old by the time they are forty. Be deadly serious in everything: the man never makes jokes, except when pretending to be funny. Great narrowness of intellect and a good deal of spite. Model yourself on some famous critic or other. Boundless passion, but without the strength to express it: a voice that cracks when he loses his temper. The extremely high notes are of course only vehement or ridiculous speech accents, not singing. Please pay close attention to every instruction, and keep exactly in time with the orchestra when you perform the part.
Your devoted servant
Richard Wagner
Source: Selected Letters of Richard Wagner, trans. and ed. Stewart Spencer and Barry Millington (W. W. Norton & Company, 1988), No. 413