If you love Bach – and who doesn’t? – Birmingham was the place to be this weekend, for a delicious series of concerts, lectures and discoveries at the Town Hall and Symphony Hall under the heading ‘Bach: A Beautiful Mind’. For Laurence Cummings, it was a chance to come home, as he was brought up in the city and reminisced about his previous Town Hall performance, playing double bass at age 18 with the Midland Youth Orchestra.

Now, as he directed the Orchestra of the Age of Enlightenment from the harpsichord, there was a democratic feel to the proceedings, an atmosphere of equality and partnership. Part of the ethos of this refreshingly creative ensemble is after all not to have a single conductor in charge, with the result that the director at any given time merely has a leasehold on his players.

Nevertheless, the harpsichordist played a key role in the interpretation of these intimate chamber pieces. Bach himself was a masterful keyboard player and improviser, indulging in the art of persuasion by decorating his melodies with a species of mathematical maze, as well as using the instrument to shape phrases and provide harmonic support. Considering his seated position, Cummings achieved this in rather animated fashion, and the resulting relationship with the other players was a joy both to listen to and watch.

The harpsichord took on an elevated role, though, in the Brandenburg Concerto no. 5. Composed at a restless period of Bach’s life, after his then patron Prince Leopold married a woman who didn’t care for music, the series of six concertos could be labelled an elaborate job application, dedicated as they were to the Margrave of Brandenburg. The unique selling point of the fifth is that the harpsichord was scored as a soloist (along with violin and flute). The first Allegro features something akin to a jazz riff for the harpsichord, and Cummings tackled this free fantasy with gusto, playing with our imaginations. Frankly, I don’t know how he kept up the breakneck onslaught of notes. Just when the cadenza seemed to be reaching a conclusion, off he’d go again. Mesmerising.

The central Affettuoso was the responsibility of the three soloists, although the harpsichord reverted to some extent to its supporting role, allowing a tender, sighing conversation to develop between Matthew Truscott on violin and Lisa Beznosiuk on flute – a period version of the instrument with a subtle birdsong quality. Their playing was controlled yet full of emotion, and so attuned were they to each other that it seemed as though they were completing each other’s sentences.

Truscott certainly earned his keep this evening, not only serving as orchestra leader and shining in the Brandenburg concerto, but also starring in the Violin Concerto in E major. This is one of just three Bach violin concertos to survive in their original form, which are apparently less virtuosic than Bach’s pieces for unaccompanied violin – but there was still plenty to keep the audience’s attention. The sunny, joyful E major key of the opening movement gave way to the relative minor for the Adagio, with its expressive, weeping quality, then back to major for the sublime comfort of the Allegro assai. Along with the exquisite sound, Truscott’s body language was eloquent, at times swaying into the phrasing or stooping to accentuate a change in dynamics, before resuming his full – and considerable – height. In the closing passages of the piece, he fleetingly turned his back on the audience altogether from time to time, for a closer interaction with his colleagues, I presumed, and perhaps because he’d become sufficiently relaxed by then. Given the strengthening of the connection, I rather wished he’d dared to do more of that throughout. Richly deserved, he received very warm applause from audience and orchestra alike.

Sandwiching the concertos in this neatly balanced programme were two orchestral suites, both in D major and sharing other characteristics too: regal themes, dance movements and the later addition of trumpets and timpani, creating exciting textures. A sense of perpetual motion with myriad semiquavers in complex counterpoint was accented with a stately, stirring quality. The exuberant Réjouissance concluded both the Orchestral Suite no. 4 and the evening ‘in the company of a genius’. The OAE’s vitality had proved to be a perfect partner to this joyous, life-enhancing music.