“A musician who has chosen this theme as an introduction to his love drama has the principal problem of how to restrain himself, since the theme is inexhaustible.” Wagner goes on in this letter to his lover Mathilde Wesendonck to outline the immense range of emotions that are involved, in true 19th century fashion. He was writing about the Prelude to Tristan and Isolde, and although (as often with Wagner) the written style is rather over the top, it is essentially accurate. The music truly does move along its prescribed path. Wagner combines an upwards moving chromatic motif that is the symbol of desire (and of the erotic) with the descending chromatic motif that for centuries had been a symbol in European music for sadness. At the very beginning of the work, the two themes are joined by a chord, which musical historians have christened the Tristan Chord. It is not the harmony itself that makes it so special (a diminished triad with a minor seventh), but rather the way Wagner utilises it and leads the phrases. The tension is never resolved – or rather, as the music appears to lead to resolution of the inherent harmonic tension, the parts move on to create further tension. It creates the sensation of a basic tonality, A minor, but without ever actually saying so explicitly. It is this that gives the Tristan music its magical power and exceptional effect. An indication of just how influential it was can be seen in the case of the French composer César Franck, then a composition pupil: he became physically ill during the performance of the Prelude and fainted from the beauty of it all…

As generally with Wagner, musicologists refer to individual motifs in Tristan by name. These names are not Wagner’s but are often accurate. The most important motifs in the prelude (in their order of appearance) are “Desire”, “Look of love” and “Liebesentbehrung” (this latter having no adequate translation into English). Just before the climax comes the “Todestrotz” motif. Traditionally in the concert hall, the prelude is connected to the end of the opera. This finishing section is actually nothing other than a kind of quotation from the middle of the opera. At the end of the third act, Isolde recapitulates the immense climax from the second act, but this time, without any dramatic break. The music rests in a B major chord, which indicates final consummation – the two lovers are together forever in death. In the orchestral version naturally the vocal lines are taken by instruments – in all other particulars however, this version faithfully follows the original.