At this distance in time, the mountain range of 20th-century modernism seems uniformly beautiful, and ideological distinctions no more applicable than to a range of peaks in the Lake District. Sibelius’s introspective Symphony No 4 (1911), Schoenberg’s explosive cabaret Pierrot Lunaire (1912), Nielsen’s “Inextinguishable” Symphony, No 4 (1916), and Berg’s restlessly intricate Lyric Suite, for string quartet (1926), can strike you as equally marvellous harbingers of a new musical age, and it matters not whether one is tonal, another atonal, the third serial. All four received outstanding performances over the past couple of weeks in three London concerts, one of which I will count among my most satisfying musical experiences.

It was part of a Barbican series celebrating the artistry of the pianist Mitsuko Uchida: not actually held at the Barbican in this case, but at its adjunct, LSO St Luke’s, the elegantly converted Hawksmoor church on Old Street, whose airy but acoustically engaging Jerwood Hall allows the audience intimate aural contact with the performers. That attribute was fully exploited by the concert Uchida had devised, a kind of superior soirée. She was joined by some superior American musicians — the Brentano Quartet, the flautist Marina Piccinini and the clarinettist Anthony McGill — as well as the German actress Barbara Sukowa, for a programme that began with the Lyric Suite, ended with Pierrot Lunaire and brought the luxury of Uchida by herself in Schubert’s Four Impromptus, D899.

Her artistry is a powerful force, but she has a delicacy of spirit, a profound reflectiveness, a sort of questing probity, not ideally served by large, impersonal halls. To hear her in vivid close-up, as though she were playing for us individually, in our homes — and playing pieces such as these by Schubert, in which power and lyric delicacy are in continuous dialogue — was a revelation indeed. Just as deeply captivating was the Brentanos’ account of the Berg. When musicians have this degree of attentiveness, this freedom and accuracy of phrase, and startling unanimity of purpose, there is no mistaking it. The work is at once graphic and cryptic, ecstatic and desolate, intellectual and pitilessly gut-wrenched, and the Brentanos resolved all antinomies. I felt Berg’s text had never been clearer.

As for the realisation of Pierrot Lunaire, it sent one home dancing on air. Uchida, of course, took the piano part, and a discreet directorial role, and her elucidatory intelligence shone through the whole, not that the two Brentano string players and two wind players were lacking in that quality. The standard of performance was almost absurdly high. Even the insatiably inventive Schoenberg’s flow of information could not adequately stretch these musicians, or so one fancied. And to their immaculateness, Sukowa, the “Sprechgesang” (speech-song) reciter, passing from one player to another, performing from memory, added her blazing histrionic contrast.

Imprecision is built into her part. She has pitches and rhythms to deal with — and they matter — but must somehow depart from them in the act of registering them, a ticklish business that Sukowa managed rather well. In this strange ambiguity, the deliberate dirtying of an obsessively meticulous new order, one can perhaps see the birth of the avant-garde. Certainly, without Pierrot, Boulez’s Le Marteau sans maître or Maxwell Davies’s Eight Songs for a Mad King would have been impossible. Despite the homecoming motif and eerie hints of tonality at the end of Pierrot, the work is looking in quite another direction.

Sibelius’s Fourth Symphony, on the other hand, stands in its modernist austerity alone. The bare textures and stark foreshortening of this pained but wonderfully thought-out structure rarely fail to grip an audience these days, and the Philharmonia Orchestra’s Queen Elizabeth Hall rendering, under the Finnish conductor Jukka- Pekka Saraste, was both masterful and hypnotic.

The American-born Joseph Swensen, who has Nordic blood (as well as Japanese), made a strong impression conducting the BBC Symphony Orchestra at the Barbican in Sibelius’s early tone poem En Saga and the Nielsen symphony, as well as in Mark- Anthony Turnage’s Beckett- inspired, hard-driven but exotically coloured soprano-saxophone concertante Your Rockaby (with Martin Robertson a skilled soloist). I was surprised that neither the programme-note writer nor the announcer of the Radio 3 broadcast next evening saw fit to mention that the whole point of the Inextinguishable is its continuous struggle, across four linked movements, to achieve the key of E major. You can clearly hear at the end that we have arrived at a new and positive place, and you don’t need perfect pitch to know that this is a bright new key. But it would have been useful to have been given this key, in every sense, to Nielsen’s amazing, tumultuous art of pure process.