Mozart's stray concert and opera arias are being rounded up this year as never before: Emma Kirkby's recital, recorded in 1988, has been saved for the great gathering-in and, on the whole, it has been worth waiting for. The selection provides fair insight into Mozart the working-composer. The shameless display of ''Aer tranquillo'' written, in Il re pastore, to impress the visiting Archduke Maximilian Franz, leaves Kirkby's voice a little matt of surface at its highest and its fastest. ''Nehmt meinen Dank'', on the other hand, written for one of Aloysia's farewell concerts as she set out on tour, sees Kirkby charming her way through its short, curtseying phrases in the gracious company of flute, oboe, bassoon and pizzicato strings.
Hogwood's Academy plays thoughout with sentient vigour. For ''L'amero, saro costante'', Christopher Hirons steps out to provide an affecting solo violin confidant for the leaning, sighing vocal part with its irresistible descending trill of a tiny cadenza. And in ''Ch'io mi scordi di te'', the interplay of Kirkby's voice, orchestra and Steven Lubin's fleet-fingered fortepiano is deeply satisfying.
A particularly piercing oboe needles its way into the heart of the tragedy of ''Ah, lo previdi''. More a full-blown, 11-minute scena for Andromeda, this, too, was written for Aloysia, and Mozart instructed her, ''Pretend you are really her!''. Kirkby certainly does, from her anguished accusations to Prince Eristeus to her oboe penetrated cries of ''Va!''. Only a lack of darker shadows, fuller depths of tone, frustrate her purpose. It is this vocal limitation that forms the unique profile of Kirkby's voice, which, in the end, wearies the listener. In Zaide's ''Trostlos schluchzet Philomele'' even Kirkby herself has to relinquish finally the brightness at the voice's core, and in doing so reveals that it cannot live by that alone.'