Composer Jake Heggie and librettist Gene Scheer have been busy lately. They are at work on Moby-Dick, which the Dallas Opera will premiere two seasons from now after it moves into the new Winspear Opera House. Meanwhile, the Houston Grand Opera is performing their latest completed work, Last Acts.

Last Acts is a chamber opera for three vocal soloists and 10 instrumentalists (one of whom, during the current run, is Heggie himself on piano). It’s about a prominent, self-centered actress and her two adult children. Her son, who is gay, has a lover who is dying of AIDS. Her daughter is an alcoholic who is married to a faithless husband. The siblings are close, but they have problems with their mother. An unseen (and unheard) presence is their long-dead father.

This family drama is played out over 20 years, with the three acts taking place in, or soon after, three Decembers: in 1986, 1996 and 2006. The audience, and the actors, view the relationships from changing perspectives.

Although Last Acts has a little too much of the flavor of soap opera, it works fairly well as theater. At least I was caught up in the story on Sunday afternoon, partly because I hadn’t read the libretto beforehand and wasn’t sure how it was going to turn out (how often do you get that in opera?).

The cast — Frederica von Stade as the mother, Keith Phares and Kristin Clayton as the siblings — was quite effective dramatically, somewhat less so vocally.

Heggie’s musical score has characteristics of many modern American operas. It establishes a mood that complements the story well but the vocal parts are recitative-like and never really take wing (a soaring vocal line must be the hardest thing for a composer to bring off). In fact, the orchestral writing tends to be more attractive, surely not a good thing in opera.

The stage picture is appealing (the orchestra is onstage, sometimes behind a scrim, and the singers at times move among the instrumentalists, who are dramatically placed). The lighting is subtle and strong, although it made the projected text hard to read at the mezzanine level, from which I viewed one act (even though the opera is in English, the projections help). The performances are in Cullen Theater, the smaller of the venues in the Wortham Theater Center.

Incidentally, Heggie and Scheer have decided to rename Last Acts. When the Houston run ends on March 15, it will be known thenceforth as Three Decembers.