Otto Klemperer was born on 14th May 1885 in Breslau, Silesia (now Wroclaw, Poland) and died on 6th July 1973 in Zurich and hence next year we mark 40 years since his passing. Although disabled by a stroke suffered whilst a brain tumour was being taken out he became a world-renowned conductor whose recordings were the touchstones for the EMI catalogue. Besides the classics of the symphonic repertoire he recorded a number of operas including four by Mozart.

His recording of Don Giovanni was made in June and July 1966 and has been a favourite of many since its release starring as it does Nicolai Ghiaurov a suave young Bulgarian bass then aged 36.

The opera was cast from strength with Nicolai Gedda, Christa Ludwig, Walter Berry, Claire Watson, Franz Crass and Paolo Montarsolo; in the role of Zerlina was the superbly talented Mirella Freni, then aged 31, whose performances as Mimi in an EMI recording and a film with Herbert von Karajan had attracted worldwide attention.

Quite by chance when various tapes were being sorted in EMI’s Abbey Road studios some containing rehearsals, actual takes, play-backs and discussions in the control room were found. This remarkable discovery prompted EMI to commission Jon Tolansky, well-known for his remarkable insights into recording and who has supplied a number of programmes for EMI Classics, to listen to the tapes and use them to make a “documentary in sound” which would demonstrate how parts of this classic recording was made.

He chose the Overture, thereby showing Klemperer’s close attention to orchestral detail, and the opening of Act One Scene Three where the peasants are celebrating the forthcoming marriage of Zerlina and Masetto which brings in two soloists and chorus. Zerlina’s beautiful aria “Batti, batti o bel Masetto” is then recorded with Klemperer clearly adoring – as we all do – Freni’s seductive singing.

The selection is completed with Don Giovanni’s serenade from Act 2 “Deh vieni alla finestra”.

This invaluable document captures not only Otto Klemperer’s rehearsals during his recording sessions for Mozart’s Don Giovanni, but also playback listening auditions in the control room at which Dr Klemperer, Mirella Freni and Paolo Montarsalo were present together with producers Peter Andry and Suvi Raj Grubb and balance engineer Robert Gooch. All this material was discovered at EMI’s Abbey Road Studios by Allan Ramsay, who has mastered this CD and the CDs of the complete opera recording. Following is a guide to the content.

Tracks 1 and 2: the Overture rehearsals and recording takes reveal how meticulous and alert Klemperer still was at this late stage of his life, contrary to what has sometimes been stated.

Track 3: the first rehearsal and recording take of Giovinette, che fate all’amore illustrates Klemperer’s demands for lively colour, character and precise rhythm, and in pursuit of this he criticises the chorus at the end.

Track 4: we hear the mutual respect Dr Klemperer and Mirella Freni had for each other as Ms Freni explains a point to him about the necessary difference in staccato and legato singing at two specific moments in the first and second parts because of the words: because of the consonants in the first part, only the second time round, where there are vowels, can legato singing be possible.

Track 5: in the second rehearsal and recording take of Giovinette, che fate all’amore, Dr. Klemperer has a little mischievous fun at the expense of the production team, and we also hear how he admired Mirella Freni’s singing.

Track 6: during the playback in the control room, a decision is made on the recording take of Giovinette, che fate all’amore that is to be used.

Track 7: in Batti, batti o bel Masetto, there is a telling example of Klemperer wanting delicacy and expressiveness from the orchestra, confounding claims in some quarters that he was not concerned with expression.

Track 8: during the playback of the Batti, batti o bel Masetto recording take, Klemperer asks Mirella Freni if she can sing one phrase in a particular way.

Track 9: we first of all hear Dr Klemperer telling Hugh Bean, the leader of the New Philharmonia Orchestra, how Nicolai Ghiaurov’s name should be pronounced and how he admired Mr Ghiaurov. This is a delightful little spontaneous exchange that has been captured by the microphone, and it shows that beneath Klemperer’s rather severe exterior he was approachable and personable. There are then several takes of Don Giovanni’s Serenade, in which we hear Mr Ghiaurov asking for several repeats until he was happy, with Klemperer accommodating him very co-operatively. We also hear how there were a number of repeats for the mandolin until both Klemperer and Mr Ghiaurov were fully satisfied. At one point there is a brief suggestion of how terrifying Dr Klemperer could be, but the session continues without incident.

Altogether this is a highly revealing picture of how Dr Klemperer was a true opera conductor – in his pursuit of theatrical action and character, and in the way he balanced his own precise demands with his flexible accompanying of the singers’ individual interpretations. The document is also an invaluable record of his perfectionism for precision, rhythm and ideal balance of details in the orchestra – and a vivid snapshot of his occasionally very amusing personality.