As far as countertenors go, there can be few names as likely to draw a crowd as that of the magnificent Andreas Scholl. With his name atop their tickets, underlined by those of soprano Klara Ek and the Academy of Ancient Music, the audience members of this Friday night concert at London’s Barbican Centre were certainly expecting a treat.

I know I shouldn’t, but usually I find myself ever-so-slightly (and only momentarily) startled at hearing the inimitable sound of a countertenor issuing from the vocal chords of a grown man. For Vivaldi’s Stabat Mater, which opened the evening’s music-making, however, it was hearing the Barbican Hall filled with the sound of period instruments that provided the sonic shock; accustomed to hearing either amplified or symphonic music in this wonderful concert hall, the nowadays familiar sound of gut strings regained some of its almost-alien anachronism for me as the driving rhythm that begin the piece was quite fiercely played out by a highly energised ensemble. After this initial frisson, the sound of Scholl’s pure falsetto seemed perfectly normal as it radiated effortlessly out of the still-assertive string texture.

The Stabat Mater is a highly emotive 13th-century devotional text in which the poet imagines, and asks to share in, Mary’s grief at the foot of the cross. Such a subject allowed composers an excellent opportunity to write some proper mournful yet bittersweet music, and the two Baroque composers whose attempts we heard this evening certainly did just that. After the vivid, highly wrought opening movement, Vivaldi takes a more measured, reflective approach in the second by removing the forward propulsion, replacing it with soft, marked crotchets in the violins, a soothingly fluid countertenor line and satisfying harmonic movement in the continuo part. Throughout the piece, the AAM’s upper strings were impressively expressive, their temperament ranging from comforting to aggressive – the bite of the gut strings proving particularly effective in the double-dotted penultimate movement. Furthermore, the whole ensemble was always entirely conscious of their balance and blend with Scholl’s subtleties.

Klara Ek’s soprano was the focus of the second Vivaldi work dedicated to the the Virgin Mary, his Salve Regina, which preceded the interval. After a lovely opening duet between leader/director Pavlo Beznosiuk and the continuo players, the soprano’s light, confident voice joined Beznosiuk’s violin in a beautiful imitative sequence, Ek’s superb control on the quicker notes equalling the tonal quality of her sustained ones. This far more positive prayer provoked some supremely satisfying Vivaldian harmonic sequences, and despite the continuo’s urgent immediacy in the non-stop movement of the exhortative second section, the general mood of the piece was well summed up in the soothing, pastoral sound of the final part. Again, the AAM showed its exemplary musicality in the way they achieved a perfect balance with Ek’s voice; she, in turn, expressed a captivating love for and devotion to the music, and, it seemed, its subject.

Between these two works, and at the start of the second half, a pared-down AAM performed two Concerti Armonici by the magnificently named Dutch aristocrat Count Unico Wilhelm van Wassenaer. These charming pieces, for which the Count could not, given his elevated social standing, permit himself to take credit, were composed for private aristocratic performances. It was not at all difficult to imagine Wassenaer and his peers together enjoying these works, with their stately movements quickly succumbing to lively, jovial faster ones. The ensemble worked together seamlessly, the four remaining violinists delighting in the frequent imitative interplay which abound throughout these two endearing Baroque nuggets.

Finally, the soloists joined forces for the second, more famous rendition of the Stabat Mater, that of Giovanni Pergolasi. This work is immensely and immediately striking: its opening wailing semitone clashes are iconic. Twice the length of the Vivaldi, Pergolesi’s work builds on that stunning opening phrase to encompass a wide range of musical emotions – including a bizarrely jolly-sounding (to our ears) syncopated movement – setting each verse or pair of verses to a different operatic form. It is filled with exquisite moments, highlighted superbly by another wholly dedicated performance from all the musicians on stage. Ek, in particular, performed in a remarkably musically sensitive way, recognising the difference in power between her voice and Scholl’s, and adapting beautifully.

The ensemble did here again what it had done so subtly but outstandingly well throughout the concert: they had complete control over the weight of instrumental sound, transferring it communally like the muscles of dancer, wielding the power of each dynamic gesture to bring the music alive. It was this totally integrated, shared musicality that made this concert so particularly wonderful; it wasn’t so much the presence of the headlining individual as the way every single musician worked so exceptionally as part of the collective that made this musical treat into a real delicacy.