Although he faced strong competition for this title from the likes of Roberto Stagno, Italo Campanini, Angelo Masini and Francesco Tamagno, Gayarre was regarded by many late 19th-century music commentators as being the supreme Italianate tenor of his generation.

One of his fellow workers, who heard him singing as he worked, encouraged him to join the Orfeón Pamplonés, the city's newly formed choir directed by Joaquin Maya.

After leaving the conservatory in 1868, he sang in the chorus of zarzuela productions in Madrid, but after being dismissed by the theatre manager, Joaquín Gaztambide, he returned penniless to Roncal.

Encouraged by Hilarión Eslava, his admirers, led by Conrado García, one of the founders of the Orfeón Pamplonés organized a successful recital in Pamplona which persuaded the Provincial Council of Navarre to grant him funds to pursue further studies with Giuseppe Gerli at the Milan Conservatory.

Particularly renowned for his interpretation of Fernando in La Favorita, he was also considered by critics of the time, especially in Italy, to be an excellent actor with a commanding stage presence.

[2] Gayarre's earliest successes and fame came from his performances in the major opera houses of Italy, where he created the role of Marcello in Il Duca d'Alba in 1871 and Enzo in the 1876 premiere of La Gioconda.

Gayarre also sang in Lisbon, Vienna and Saint Petersburg and toured Brazil and Argentina with the Spanish contralto Elena Sanz, a frequent stage partner, especially at La Scala.

In the 1870/71 season, at the Teatro Regio di Parma, he sang with great success in a trio of Verdi operas, I Lombardi alla prima crociata, Un ballo in maschera and Rigoletto.

On 8 December 1889 at the Teatro Real in Madrid, he appeared on stage for the last time in Bizet's Les pêcheurs de perles, where his voice cracked noticeably in Nadir's aria, 'Je crois entendre encore'.

In 1901, his grave was marked with an elaborate marble and bronze mausoleum by the noted Spanish sculptor, Mariano Benlliure.,[5] and two years later, Pamplona renamed its Teatro Principal in his honor.

The playwright and music critic George Bernard Shaw reproached Gayarre during his London appearances for displaying an excessive vibrato and "artificial" vocal mannerisms.

Their collective opinions are encapsulated by the following assessment published in the 1963 Ricordi Enciclopedia della musica:[7] Gayarre's voice was slightly guttural and at times could show hardness in the very high notes and an uncertain attack.