For many, it will be enough compensation that Malloy’s music remains as hypnotic and embracing as ever, performed faultlessly by the cast (especially Seibert) and a busy quartet (violin, cello, French horn, keyboards) under Or Matias’s musical direction. A close-harmony coda, accompanied only by a hurdy-gurdy drone, specifically recalls the a cappella wonders of “Octet” and the hushed beauty of the title song of “Natasha, Pierre & the Great Comet of 1812.” But intermittent gorgeousness is not, for me, a sufficient substitute for substance. What is “Three Houses” trying to say, or have us experience, about living through the pandemic — beyond the usefulness of eight quantities of liquor?