In Act II of Tannhäuser, Hermann, Landgrave of Thuringia, sets the theme of the singing contest that is about to take place in his hall by asking: “Can you describe love’s nature to me?” To some extent, the entire opera is an examination of two very different answers to that question. We are offered visions of extreme erotic love in the orgies of Venus’ mountain, and the pure, chaste love espoused by the courtly love poets against whom Tannhäuser must compete. Tannhäuser himself vacillates between carnality and purity, as represented by the women Venus and Elisabeth, and within the morality of the story there is, tragically, no middle way; the obvious compromise of monogamous erotic love doesn’t seem to enter the mind of any character.

Tonight’s concert performance at the BBC Proms by the BBC Scottish Symphony Orchestra came down firmly on the side of purity, although both women, Daniela Sindram’s Venus and Heidi Melton’s Elisabeth made their case strongly. Melton’s first appearance, when she greets the hall in which her beloved will soon sing again, was moving in its sheer joyfulness and her singing retained this simple radiance throughout the performance. By contrast, Sindram was wickedly sensual in her opening scene, and developed her character beyond simply a one-dimensional image of seduction, becoming not an aloof goddess, but a real woman, fighting to keep her man, as she makes ever more extravagant threats in the face of his indifference.

Without any staging to speak of and with acting kept to the absolute minimum, it was hard to judge whether the indifference of Robert Dean Smith’s Tannhäuser to Venus’ charms was intentional, or simply a case of weak singing. In the first act, he was sometimes overwhelmed by the orchestra, and seemed tired on his top notes, but he improved as the evening went on. He responded with warmth to the simple devotion shown by Heidi Melton’s Elisabeth, and showed much more passion and conviction in his angry defence of carnal love during the song contest than he had done in the presence of Venus. He was even stronger during the despair of the final act, when he recounts the devastating story of how he was refused forgiveness by the Pope, and is tempted again by Venus.

Matching Heidi Melton’s warmth and purity was Christoph Pohl’s generous portrayal of her faithful lover, the courtly love poet Wolfram von Eschenbach. Wolfram personifies the quietly noble love of the troubadour for his lady, the ideal that Tannhäuser is expected to match, and his lament in Act III when he foresees her death, “Da scheinest du, o lieblichster der Sterne”, was gorgeous. Pohl has a rich, lyrical baritone voice that filled the Albert Hall with ease. There were also good performances from tenor Thomas Blondelle as the angrier poet, Walter von der Vogelweide, and Ain Anger growled out the low bass role of the Landgrave authoritatively. The all-too-brief appearance of Hila Fahima as the shepherd boy, after Tannhäuser escapes from the heady pleasures of the Venusburg, also deserves a mention: her freshness of tone gave the first hint that purity was going to win here.

In the absence of staging and acting, of course, the orchestra have to work extra hard to set the scene, and the BBC Scottish Symphony rose to the occasion, from the quiet warmth of the opening horn motif through to the climaxes that end each act. The brass section, always so important in Wagner’s orchestral writing, were strong, and with good tone, but never overpowering. The offstage brass and wind, positioned around the galleries of the Royal Albert Hall, were thrilling but a special mention has to go to cor anglais player James Horan for his delicious pastoral accompaniment to the shepherd boy’s aria.

We’re never really told how or why Tannhäuser has found himself trapped in Venus’ clutches, and the plot has many unsettlingly unanswered questions and gaping holes. Donald Runnicles’ approach patched over these holes and played strongly on the theme of redemption; the moral code of the opera’s mythical-medieval setting is taken at face value, without judgement. The crowd scenes, sung by the Concert Association of the Chorus of the Deutsche Oper Berlin, were forceful, but never allowed to descend to mob anger or smug sanctimony – the chorus are outraged by Tannhäuser’s behaviour but they keep open the possibility that he could be redeemed. Their final chorus swelled with honest delight at the sign of Tannhäuser’s eventual forgiveness, and as the famous melody from the overture grew to its climax, it would have taken a hard heart indeed not to rejoice with them.