LONDON – Much of the Curtis Institute staff migrated as far away as possible from its touring orchestra for the second half of the ensemble's Friday concert here at Cadogan Hall. The upper gallery was the only place they might not be consumed in the Straussian vortex that was Ein Heldenleben – a grandiose work not typically heard in this 900-seat Christian Science church-turned-concert hall.

Though it's an increasingly famous venue thanks to the BBC Proms chamber music concerts broadcast from there during the summer, the hall offers nothing more bombastic on its schedule for the next month than the mid-size Shostakovich Symphony No. 5. So after a sunny day off in London with no airports or passport lines, the Curtis Symphony Orchestra gave listeners much to wrap their ears around.

But a day off isn't entirely a gift.

Many of the musicians arriving late Friday afternoon at the venue, only a block from festive Sloane Square, hadn't seen their instruments since Wednesday's Dresden concert. This isn't a matter of separation anxiety. Hornist Amit Melzer managed to keep his instrument with him and does maintenance practice, grabbing 20 to 30 minutes whenever and wherever he can. And with good reason. "After a flight, your lips can be a little swollen," he said.

The rule of thumb is that if you take a day off, you’ll feel it at the next concert. The way bassist Braizahn Jones explains it, concert performances are part muscle memory, and that memory slips without access to the instrument. Sometimes he doesn’t even hear the deterioration himself.

The reason for the separation: While musicians fit easily into airplanes, basses and harps do not, and arrive by truck after marathon driving sessions. Because Cadogan Hall is located in the largely residential Belgravia section of Central London, the narrow load-in street, Sloane Terrace, had to be cleared of parked cars in advance, arranged by tour manager Arnold Klugkist for a relatively modest fee of 250 British pounds a day. But because of limited backstage space, the empty harp cases had to be stored back in the truck during the concert, while the drivers had some shut-eye before the nighttime drive to the next tour stop, Salzburg.

Inside the hall, music industry bigwigs and Curtis alumni sipped bubbly drinks. Alumnus Matthew Rose, an opera bass who rehearsed  Britten's A Midsummer Night's Dream all day, arrived for the concert out of  loyalty. "I went in [to Curtis] with very little and left with a career … and what I needed to do the job," he said. In fact, he was tentatively tapped to do a last-minute save in the recent Metropolitan Opera simulcast of Der Rosenkavalier, though the ailing singer recovered in time.

Olivia Ma, who runs her own management agency that has toured the Russian Mariinsky Orchestra, Ballet and Opera for decades, is determined to bring the Curtis Symphony Orchestra to the Far East based partly on what she heard in Berlin. "Audiences there deserve to hear them," she said.

Said Curtis president Roberto Diaz, "We still have to digest this trip first."

In this fifth concert of the nine-concert tour – the first multi-city European jaunt since 1999 – what exactly was the orchestra offering? Curtis is a different beast than, say, the Philadelphia Orchestra with its many decades of tradition. The forthright Curtis strings don't have infinite variety of shading or multi-level depths. The sense of ensemble is more learned than instinctual. But the no-sweat confidence and energy of the orchestra's playing at Cadogan Hall had a wall-of-sound infectiousness. And if musicians can acquire depth by osmosis, they have an ideal collaborator in Peter Serkin, soloist in Brahms' Piano Concerto No. 1.

Having won a Grammy Award at age 19, the 69-year-old Serkin has reached a point in his career where people sometimes talk about his playing not being what it once was. Though always a reflective, searching pianist whose tone quality has a dignified spiritual radiance, Serkin has a  current view of Brahms that can in some ways be boiled down to the question of "Why?" – mostly around the nature of fate.

But the kind of performances that have been building on this tour have a leonine quality not often heard from him in past decades. That reached a new peak on Friday in London. The poetic "why" had a healthy balance of extreme existential anguish. At times, his performance was so emotionally candid that you couldn't believe you were hearing it in such a public place. He's everything he ever was – and more.

Ahead on the Curtis European tour are Salzburg, Vienna, and two dates in Poland — the final one, on June 2, with the orchestra playing Krzysztof Penderecki’s Concerto doppio at the Penderecki European Centre for Music in Luslawice and probably in the presence of Penderecki himself. Nobody seems intimidated.

Conductor Osmo Vanska does have a question or two about the score. "I might ask," he said, "even if it's too late to change anything."

David Patrick Stearns has been touring this week with the Curtis Symphony Orchestra in Europe. He will rendezvous next week with members of the Philadelphia Orchestra on the Mongolian leg of the Philadelphians' Asian tour.