The Big Question: Why is Wagner's legacy proving so bitter both to music and to his family?

Why are we asking this now?

On Sunday a memorial service will be held in Bayreuth in Germany for Wolfgang Wagner, grandson of the composer Richard Wagner, who died on 21 March aged 90. Wolfgang Wagner ran the Wagner Festival at Bayreuth, the annual celebration of his grandfather's operas, from 1951 to 2008. Now it has been revealed that his son, Gottfried, has not been invited to the memorial service – the latest twist in a long-running family feud – and the German Chancellor and Wagner-lover Angela Merkel may be called on to intervene.

What exactly has divided the family?

Some distinctly operatic questions of dynasty, power and influence; specifically, the leadership of the Festival. Wagner founded the festival in 1876; on his death his son Siegfried succeeded him, along with Siegfried's English-born wife, Winifred. Their sons Wolfgang and Wieland took over in 1951, with Wolfgang sole director after his brother's death in 1966. He retired, aged 89, on condition that the post passed to his daughter, Katharina, who was only 30. She and her half-sister, Eva Wagner-Pasquier proposed to run the festival together. Wieland's daughter, Nike, contested this, proposing a directorship shared with the respected director Gérard Mortier. Eva and Katharina won.

Why was there no role for Gottfried Wagner?

The black sheep of the family, allegedly for advocating that the family should face up to its past links with the Nazis, Gottfried has been persona non grata in the dynasty for some 20 years; apparently he was informed that his father would only accept a reconciliation were Gottfried to renounce his autobiography, Twilight of the Wagners: The Unveiling of a Family's Legacy.

Who was Richard Wagner?

One of the most important composers of the 19th century, Wagner was born in 1813 and spent years struggling for recognition, including a spell as a revolutionary in Dresden, which he fled during the May Uprising in 1849. He wrote his own opera libretti, influenced variously by Marxist politics, Schopenhauer and traditional legends such as the sagas of the Norse gods (in the Ring Cycle), the story of Tristan and Isolde, and the Knights of the Grail (in Lohengrin and Parsifal). In 1864 King Ludwig II of Bavaria elected to become his sponsor, enabling Wagner to follow his wildest dreams and to build his theatre at Bayreuth. He left his first wife to elope with Cosima von Bülow, wife of the conductor Hans von Bülow and daughter of the composer Franz Liszt, whom he married in 1870 after the births of several children.

Why is his music so important?

Wagner's operas exist on a scale of unprecedented ambition and employ concepts that transformed both the nature of the artform and the approach of later composers. Instead of the opera progressing through individual arias, duets, etc, Wagner composed in ongoing, unbroken spans of music, its fabric woven out of leitmotifs – recurring themes symbolising characters, ideas or qualities, which are transformed according to the drama. This idea revolutionised compositional methods. Also, he extended "tonality" (musical keys) so far that early 20th-century composers like Schoenberg and Stravinsky decided that the traditional systems could go no further and began to seek alternatives.

What has caused Wagner's reputation for anti-Semitism?

Wagner's notorious pamphlet Das Judentum in Musik – "Jewishness in Music" – is a stream of anti-Semitic bile against Jewish musicians. It was originally published under a pseudonym in the Neue Zeitschrift für Musik in 1850, and in 1869 was republished and expanded under his real name. Much was inspired by personal grudges. Wagner had once sent the draft of a symphony to Mendelssohn, conductor of the Leipzig Gewandhaus Orchestra, but it was rejected. He was also jealous of the composer Meyerbeer, who was Jewish, immensely popular and extremely rich – although Meyerbeer had helped him generously.

Musicologists argue about whether Wagner's operas include anti-Semitic elements; the character of Mime in Siegfried is sometimes said to be an anti-Semitic caricature, but others disagree. Hans Sachs's monologue in Die Meistersinger von Nürnberg extolling the supremacy of German art can feel uncomfortable with hindsight, but seems to contain nothing overtly anti-Semitic.

What did his appropriation by the Nazis involve?

Wagner's pamphlet does not seem to have been widely read, but is probably responsible for Hitler's oft-quoted claim that "there is only one legitimate predecessor to National Socialism: Wagner". But the link between Wagner and the Nazis was strengthened by Winifred Wagner, who adored Hitler; allegations abounded of an affair between them, not implausible since Siegfried, Winifred's husband, was gay. Wagner's music was often played at Nazi rallies (though Beethoven's was also) and by attending Bayreuth regularly and insisting that his colleagues did likewise even if they disliked the music, Hitler perpetuated the idea of Wagner as a figurehead for the Nazis.

Can the politics and the music be separated?

Yes: Wagner-lovers the world over do so every day, and most succeed. Prominent Wagner enthusiasts, in addition to Mrs Merkel, include Jewish musicians such as the conductors Vladimir Jurowski and Semyon Bychkov.

Nevertheless, for some the association remains unpalatable. The playing of Wagner not only at Nazi rallies but also by concentration camp orchestras while Jews were sent to their deaths has given rise to Wagner's unofficial ban in Israel.

The conductor Daniel Barenboim is prime among those who have attempted to break this taboo, declaring that while nobody should have to listen to music that carries terrible associations, they also should not prevent its enjoyment by others who do not share those memories. When he conducted the Prelude and Liebestod from Tristan und Isolde as an encore in Jerusalem in 2001, some audience members applauded, some walked out and heated discussion later ensued.

How important to Germany is Bayreuth?

It's widely regarded as Germany's most important opera festival, yet also it is quite niche – perhaps its true importance is disproportionate to the size of its internal scandals. As Wagner's own theatre, it is of course a focal point for international Wagnermania – tickets are so sought-after that they are allocated by ballot. Bayreuth's chief significance in the musical world is that it's the one place where operas can be heard in the exact conditions that Wagner intended. Notably, the orchestra pit is covered so that the orchestral volume is reduced and the singers need not "shout" to be heard.

Can the Wagner family be reconciled?

Were they to undergo a thorough truth-and-reconciliation process – as Tony Palmer's recent film about the family for The South Bank Show advocated – there might be some chance. And if the running of the Bayreuth Festival were to be awarded to a disinterested professional festival intendant instead of a Wagner, that might also ease the path to a quieter life. But as long as the Wagners keep the directorship in the family, the past is not comprehensively exorcised and the feuding is perpetuated, reconciliation seems unlikely.

Can Wagner ever be seen as just a great composer?

Yes...

* His music is so beautiful and so important that its significance overrides his personal views

* Leading musical figures, including some who are Jewish, dissociate the music from its composer's politics

* Musicologists debate whether the operas have anti-Semitic elements, but the general view is that they don't

No...

* It is impossible to forget about Wagner's notorious pamphlet 'Das Judentum in Musik'

* Hitler's enthusiasm for Bayreuth means its place in history is tainted

* TV and movies often use Wagner in their soundtracks to represent the Nazis, so the two remain linked in the public consciousness