The four operas of Richard Wagner's cycle Der Ring des Nibelungen together take about 15 hours, which makes for several records, tapes, or CDs, and much studio time.
[1] Although Solti's was the first studio stereo recording, the cycle had previously been recorded live in stereo by Decca engineers at the Bayreuth Festival in 1955 under the baton of Joseph Keilberth.
Although unavailable for over 50 years, this cycle was finally released in 2006 on CD and vinyl by Testament.
When John Deathridge carried out a follow-up review for the programme in 1992, he favoured parts of the Goodall, Haitink and Boulez cycles for individual operas and Levine overall.
These include: The Boulez, Barenboim, Zagrosek, and Haenchen performances are also available as audio recordings.