‘And what will it be like repeating this in the Royal Festival Hall?’ I asked Simon Rattle after he had conducted a blazing account of Walton’s Belshazzar’s Feast in Birmingham’s Symphony Hall, its adjustable acoustic opened up to its resplendent best. ‘A bit like driving a car into a brick wall at 60 mph’ was the baleful reply.

This live 1964 Royal Festival Hall recording of Verdi’s Requiem brought that conversation back to mind. How dry and aggressive the sound is in comparison with that of an earlier Giulini performance – a 1963 Promenade Concert recorded live in the Royal Albert Hall – which BBC Legends released four years ago.

The 1963 Proms performance preceded the main sessions for Giulini’s celebrated EMI studio recording. The Royal Festival Hall performance followed the completion of the recording in April 1964. Of the three, the Royal Albert Hall account has the best sound (spatially, the hall might have been built for the work) and is superbly engineered. Even though it was made in mono, the Proms recording sounds rounded and stereophonic. The studio recording, notoriously, is subject to a certain amount of residual distortion in the big choral tuttis. It also has a somewhat manufactured air alongside the free-flowing live account. Which is not to deny it its status as a classic of the gramophone; as Giulini concedes in an interview with Michael Oliver which has been added to this latest set, all recordings have their limitations.

That said, the studio performance is infinitely preferable to this live Festival Hall account whose acoustic does no favours to a solo quartet that already sound ill-matched and under-rehearsed. Grace Bumbry is in lustrous voice but there is a hardness to Ilva Ligabue’s tone which I don’t recall from hearing her live. Of the three tenors – Nicolai Gedda (EMI), Richard Lewis (RAH) and Sándor Kónya (RFH) – Kónya is by some distance the least distinguished in both manner and tone. As an ensemble, the Festival Hall team works far less well together than Lewis, Amy Shuard, Anna Reynolds and David Ward in the Royal Albert Hall performance.

What is common to all three performances is the matchless power and integrity of Giulini’s conducting and the comparably fine singing of Wilhelm Pitz’s Philharmonia Chorus. Even now, the choral work more or less defies belief: words and music made manifest in a way that takes our (though obviously not the chorus’s) breath away.

As for the two live BBC recordings, the Royal Albert Hall version is clearly the one to go for, not least because the set generously includes a memorable Edinburgh Festival performance of another work close to Giulini’s heart, Schubert’s Mass in E flat, D950.