Gundula Janowitz officially retired from the stage in 1990 and, according to most accounts, gave occasional recitals until around the middle of that decade. It might come as a surprise, then, to find that her final recital actually dates from September 1999 – and that it was captured for posterity.

It’s a wonderful surprise, too, since the singer (who recently turned 80) is in remarkably fresh voice throughout. There’s a certain loss of bloom, inevitably, and an occasional brittleness of intonation, but the unique sound is unmistakable, the delivery still clear and confident. First Hand Records’ remastering of the unofficial recording, captured outdoors in Athens’s Herodes Atticus Odeon, is impressive too: a little reverberant, perhaps, with the sound of Charles Spencer’s piano a touch clangorous, but beautifully balanced and direct – and with very little extraneous sound.

The programme has clearly been selected with the greatest care: here are songs with a certain valedictory potential that is brought out by the occasion as well as by an interpretative approach from Janowitz that is non-interventionist and leisurely. It’s almost as if the singer herself is reluctant to let go, needing occasionally to be coaxed along by Spencer’s robust piano-playing.

The opening line of Schiller’s ‘Die Götter Griechenlands’, lamenting the passing of a world of beauty, seems doubly apt as a starting point; while few singers of any age today would be able to match the purity of tone and warmth Janowitz can still bring here to the opening of ‘Der Fluss’. A highlight is a particularly moving performance of the substantial ‘Raste, Krieger!’ Only in a cautious-sounding ‘Der Lindenbaum’ does one detect a lack of firmness in the lower range, and there’s some understandable tiredness – at the end of what I assume was the concert’s first half – in ‘Das Lied im Grünen’.

There’s much to enjoy in the Schumann, but the second half is really all about the handful of Strauss songs, performed with wonderful breadth, serenity and integrity. At this point the voice also finds new reserves of power and luminous tone. I can’t imagine many dry eyes being left after ‘Allerseelen’, ‘Morgen’ or a tender ‘Nachtgang’ – but if there are, the final ‘Befreit’, managing to be simultaneously vulnerable and majestic, will surely put an end to that.

That song proves a hard act to follow, and FHR’s need to squeeze over 82 minutes of music on to the disc means little time to recover before an encore, ‘Die Forelle’, in which the 63-year-old soprano suddenly sounds more fallible. A last-minute change in the programme also means that we have ‘Das Rosenband’ at the start of the Strauss selection rather than the listed ‘Lob des Leidens’. Still, this is a remarkable document: a moving concert and an essential buy for any fans of this great singer.