A student of Leonardo Leo in Naples, he became Kapellmeister at the Ospedale della Pietà in Venice. In the document recording his appointment as maestro di cappella of the Ospedale della Pietà he is called 'Alessandro Gennaro Napolitano', which indicates who was born or educated or both in the Neapolitan region. Fétis claimed that he was born in Naples in 1717, but no confirmation of this is known. He was in the service of the Pietà from August 21, 1739 until May 13, 1740 when he was dismissed for lack of diligence. He was not entirely idle in this period, however, as he presented his opera "Ottone" at the Theatro S Giovanni Grisostomo, Venice, during the Carnival of 1740 and his serenade "Il coro delle muse" at the Ospedale on March 21. of the same year, interpreted by him and the students themselves. Both compositions were in honor of the Elector of Saxony, Friedrich Christian. Carlo Goldoni, who wrote the lyrics for the serenade, said in his memoirs ("Delle commedie di Carlo Goldoni", Venice, 1761) that he adapted them to the music that Alessandro had written for three earlier cantatas with texts by Goldoni, "The Nymph saggia", "Gli amanti felici" and "Le quattro stagioni". These three cantatas are also presumed to have been composed during the period 1739-40.
