Anyone who has been following this seriesand who knows opera will have been wondering when Wagner's Tristan und Isolde would come up. This revolutionary and consummately romantic opera is as good an example as you'll ever find of music expressing the erotic.

Yet I've hesitated, not as to whether I would include it, but as to just what I would say. Perhaps a brief summary of the plot will explain my hesitation.

The action takes place among the British Isles of antiquity, more or less in the time of Arthur. The Irish King's daughter, Isolde, is on a ship bound for Cornwall, where she is to marry King Mark. She is being escorted by Tristan, friend and nephew of the Cornish King. Although Isolde affects hatred toward Tristan and he indifference toward her, there is a strong undercurrent of sexual attraction in the music.They confront each other and, claiming a fatalistic world-weariness, they agree to take poison together.

Isolde orders her servant to prepare a fatal draught, but the servant secretly prepares a love potion instead. Its effects are almost immediate and the blissful lovers scarcely notice their arrival in Cornwall.

Between Acts I and II, the intended wedding does take place, however. One is left to imagine Tristan's feelings and especially those of Isolde on her wedding night. Meetings between the two are difficult, but in Act II Tristan and Isolde do manage to see each other one night while the King is hunting. They sing a famous love duet in which the sexual tension mounts in succeeding waves, just as it does in real lovemaking. The instant of release is headed off, however, by the arrival of the guard. Tristan is seriously wounded.

In Act III, Tristan is lying on the beach near his hereditary castle. He is near death, but his servant believes that if Isolde comes to him he will recover. Indeed Isolde is on her way. King Mark has learned of the love potion and has forgiven everything. When Isolde arrives, however, it is barely in time for Tristan to die in her arms. Feeling Death close by her own side, she sings ecstatically of her eternal union with Tristan in the infinity of the stars.

Anyone who can keep their eyes dry through a good performance of Isolde's last scene –- the liebestod or love-death as it is usually called –- needs to have their heart checked. And who among us has not had the experience of a forbidden love, or at least of one that is unattainable?

Still, union in death is not as popular a concept as it once was. Perhaps in our increasingly secular age the notion of any kind of life after death has lost its allure. More to the point, I think, we no longer necessarily think of erotic love as something dark, secret and forbidden.

This is a remarkable development. When I was growing up in the late 50s, the general attitude toward sex, particularly sex outside of marriage, was essentially the same as it had been for centuries. Then came the birth control pill in the early '60s and the sexual revolution that followed. People born since then, though they may have their own repertoire of sexual hang-ups, cannot imagine the weight of interdiction, regulation and shame that was imposed on the erotic impulse since time immemorial.

So what to make of the sad tale of Tristan and Isolde? Why didn't they just inform King Mark that their needs were incompatible with the roles society had assigned them and that they were going to shack up and leave him to find another bride? Surely that would have been a more life-affirming solution than the grave.

Of course, we understand that such options would not have been available. Tristan and Isolde could not alter their career paths, resort to self-help books or go for counseling. But can we really feel their dilemma? How often have you seriously felt that you would be more at one with your beloved if the two of you were dead?

People still took to that notion in my youth, say 40 years ago. Every now and then you'd read of an adolescent couple who had committed suicide in the face of some obstacle to their love. And even now we are moved by the story of Romeo and Juliet, young lovers who refused to face life without each other.

The late romantic belief in union in death is undoubtedly a corruption of the traditional Christian teachings about the love of God. Since we cannot truly know and love God in this life, we must await the next life for our fulfillment. And since the love of God is the ultimate true love, it follows that our devotion to a human lover is best proven by how closely it imitates the divine love. Or something like that.

But whether you can subscribe to Wagner's theories of love-death or not, there's no doubt that the music to Tristan and Isolde is among the most duskily steamy ever written. Though the full opera is an undoubted masterpiece, most lovers would find a purely orchestral rendition of the music more congenial to intimate moments together. The famous concert piece, the Prelude and Liebestod is particularly erotic, but rather short.

Recently Edo de Waart and the Netherlands Radio Philharmonic released a CD called Tristan und Isolde: an orchestral passion (RCA/BMG 447852). It amounts to an hour-long tone poem that wordlessly tells the story of the doomed lovers and casts a rich and passionate spell on the listener. Highly recommended.

This article originally appeared in Clean Sheets.