With a sage guide, a tour of a cathedral in sound

Christoph von Dohnanyi provided aural spacing in Mozart’s Piano Concerto No. 23 for noted pianist Radu Lupu.Stu Rosner For the boston Globe/Boston Globe

It’s been a difficult few seasons for the Boston Symphony Orchestra’s roster of distinguished aging guest conductors. Kurt Masur recently fell and broke a hip in a Tel Aviv hotel room. Once a frequent guest, Sir Colin Davis has not appeared on a BSO schedule since his last cancellation in 2011, also on health grounds. And Rafael Fruhbeck de Burgos (returning next week) was visibly frail when last seen conducting the BSO in Tanglewood.

Against this backdrop, Christoph von Dohnanyi, 83, stands out for his twinned steadiness and vitality, his sense of intellectual rigor leavened by the wisdom of experience. His visits to the BSO podium during this leaderless period have grown more frequent, and he is back again this week, this time with works of Mozart and Bruckner.

The experience quotient in fact runs particularly high on the first half of this week’s program, as the soloist in Mozart’s Piano Concerto No. 23 is the distinguished Romanian pianist Radu Lupu. On Thursday night, Dohnanyi, a no-nonsense accompanist, drew out Mozart’s orchestral textures with transparency and restraint, allowing Lupu the space to have his eloquent way with the solo line. The opening Allegro was spacious and flowing (with a masterfully turned cadenza), the sublime slow movement full of a poetic melancholy. Lupu grasps something deep about the underlying expressive grammar of this music.

After intermission, Dohnanyi led the orchestra in Bruckner’s massive Symphony No. 4. A bit of applause broke out after the epic first movement.The night was far from over. In truth it’s easy to understand the sense of disorientation that this music can visit on first-time listeners by sheer virtue of its scale. There are entire Mozart symphonies that would fit inside the enormous frame of the first movement alone, but the point is not only length as measured by the clock but the vast geography of Bruckner’s musical thinking.

Conducting from memory, Dohnanyi proved an expert if somewhat impersonal guide to that geography. Bruckner’s symphonies are of course deeply spiritual scores for some of their staunchest champions, but Dohnanyi clearly takes a different approach. Here is the professor of architecture visiting the cathedral to show visitors its beauty but not to worship. Bruckner’s musical logic was deftly unpacked in real time. There was plenty to admire: the orchestral sonorities amassed had heft but never flab, the string sound rich and full, the brasses burnished and glowing.