Why recordings come and go is one of the imponderables, but two that went have come back at an auspicious time for SF opera (and SF Opera) lovers. The 1990 Vienna Lohengrin, conducted by Claudio Abbado, is back on a pair of ArtHaus DVDs that seem to me an ideal set to prepare for October's Lohengrin at the War Memorial. And something looking conspicuously like a Teatro alla Scala house label has brought out the rarely encountered June 19, 1956 Maria Callas La Traviata in a deluxe edition Callas fanciers won't want to be without.

The vagaries of the international mails prevent me from reporting on the new Lohengrin DVD set from Bayreuth (Opus Arte), but it's the already infamous Hans Neuenfels production where the mice literally get out of the lab, and it was taped after the production's premiere, when at least Jonas Kaufmann in the title role and conductor Andris Nelsons, both in their Bayreuth debuts, made it worth suffering through. This Vienna production, by Wolfgang Weber with designs by Rudolf and Reinhard Heinrich, dates from the long-ago time when Vienna productions were by reputation conservative. But the degree to which it takes Wagner literally – no fuss about the Swan, just lights and a big prop – make it an ideal way for Lohengrin newcomers to get the work under their belts. There's plenty enough to plow through just with what Wagner provided.

More clarifications are in order here. This live Lohengrin dates from 1990, four years earlier than the audio-only DG concert performance, and with one very important cast difference. In place of a slightly over-the-hill Siegfried Jerusalem in the title role, you get Placido Domingo in stupendous voice (it was the year of the original Three Tenors concert). This is arguably the best record, in all senses of the word, we have of Domingo in a Wagner role, sung a remarkable 22 years after his debut in it, which tells both in the depth of his characterization and the musicality of his singing.

You wait what seems forever for him to come on in Act II – where has he gone? was Act I just a dream? – but when he does, he's white hot. Domingo has kept many of us so busy keeping up with his current repertoire, and vocal estate, that it's become easy to forget what a magnificent singer he was at his peak. His "Heil dir, Elsa," at the peak of the Act II ensemble, gave me a kind of gooseflesh I forgot there was to have.

Cheryl Studer, as Elsa, is far better than in the later recording, not only managing her own demanding role but contributing mightily to keeping Act II on the rails vocally onstage. The Ortrud, Dunja Vejzovic, is all over the vocal map at the beginning of the act, and you watch and listen in wonder as Studer reels her in, in a weird contradiction of what's happening in the story, over the course of their long duet.

There are strong performances from Hartmut Welker as Telramund and Robert Lloyd as King Heinrich, but this tight-ensemble Lohengrin is not dependent on any particular singer but dependent on all of them, down to the final chorister (and a striking new Duke of Brabant, a non-singing role, you won't want to miss). It's the chorus that hands in the first knock-out performance, and its contributions throughout are sterling.

This incandescent Lohengrin only adds to the mystery of why Abbado has largely kept Wagner out of his personal repertoire since. His predilection for broader tempos was yet to come, and while it never feels rushed, this Lohengrin has a high level of internal combustion. Never losing a keen feeling for the drama, Abbado draws a characteristically detailed performance that opens up this already magical score. Of the ones available now, it's the Lohengrin DVD to have.

I always wanted to like the 1955 performance from La Scala the most of Maria Callas' "recordings" of La Traviata, but the poor sound quality of even the best re-masterings of that live performance was always a problem. The sound isn't that much better in the newly re-released live performance from opening night of the next season's revival (save, perhaps, that you can hear some of the audience members better), but the fact that she and conductor Carlo Maria Giulini have had another half-year to live with the music, each other musically, and the legendary Luchino Visconti production, all have pay-offs.

The CDs are tucked into a handsome book that has a complete libretto, a lavish array of photographs of the Visconti production, a complete history of Traviata at La Scala, and intelligent essays. Still, the reason to invest is Callas' continued deepening of her interpretation of the role she was born to sing above the others.