During the final years of what many fondly regard as the real D’Oyly Carte Opera Company, when it was still under the supervision of a D’Oyly Carte family member, Patricia Leonard was the principal contralto.

Established in 1879, the D’Oyly Carte had gradually evolved into a company devoted solely to the operettas of Gilbert and Sullivan, the “Savoy Operas”. As Britain’s foremost operetta ensemble, the company maintained a unique performance style, attracting to its ranks some of the finest exponents of the genre.

Yet when the mezzo-soprano Patricia Leonard joined the company in 1972 the Savoy Operas were unknown territory for her. Born in Stoke-on-Trent in 1936 and brought up in nearby Stone, she had had piano and singing lessons from an early age. She worked as a secretary, developing her singing talent as an amateur with a local operatic society. There she met her future husband, Michael Fox (later known by the stage name Michael Buchan). Encouraged to pursue a more formal musical education, she commuted to Sheffield to study singing with Michael’s teacher, bassbaritone John Dethick, in his day one of the finest oratorio singers. Success in music competitions quickly followed, a notable triumph being the Rose Bowl at the Blackpool Music Festival when she was 20, after which Patricia Leonard was launched into a semi-professional career as a soloist in oratorio and a recitalist for BBC Radio.

When her husband decided to audition for D’Oyly Carte, she auditioned too. Auditions were a two-stage process, the first being an open audition before music and production staff at a big touring venue, the second stage being a formal audition by invitation to the Savoy Theatre where “Miss Carte” (Bridget D’Oyly Carte) and the general manager Frederic Lloyd joined the adjudication panel. Leonard was granted the second audition. Her husband had been invited, and it was only when she accompanied him that she was granted a second opportunity, though with no forewarning.

For a year she was just another chorister, but her potential was soon recognised. From her second year she was playing small roles — Leila (Iolanthe), Peep-Bo (The Mikado), Vittoria (The Gondoliers) — and understudying Mrs Partlet (The Sorcerer) and Tessa (The Gondoliers). Following the departure of Pauline Wales in February 1974 the roles of Hebe (H.M.S. Pinafore), Edith (The Pirates of Penzance) and Lady Saphir (Patience) were allocated to her. In 1975, the Centenary Season, marking the 100th anniversary of Trial by Jury, She played almost all the mezzo-soprano roles including that of Elsa in a concert performance of The Grand Duke at the Savoy Theatre.

Outstanding as Leonard was as a singer, with her rich mellow-toned voice, she was now equally respected and valued as a superb actress and comedian. As Lady Saphir she exploited the resonant lower timbre of her speaking voice in a deliberately butch “hockey-sticks” manner, suggesting in her articulation of words like “Jolly utter!” that this character might be an alumna of one of the better ladies’ colleges. Yet even more memorable was her Mad Margaret (Ruddigore). Here she was variously poignant or histrionic, one moment like Hardy’s Fanny Robin, the next like Rochester’s wife, yet infused with a sensual quality.

When the position of principal contralto fell vacant in July 1977 there were sceptics who doubted whether a popular and successful soubrette could be fully accepted in these heavier roles — but they were proved wrong. She reinvented herself with consummate skill, eschewing the more bizarre traits of these intimidating females in favour of a more balanced personification. As the domineering harridan Katisha (The Mikado), she convincingly demonstrated that the grotesque mask hid a fragile suffering woman. Nor was the soubrette ever too far away. Her Queen of the Fairies (Iolanthe), outwardly so full of composure, betrayed in tantalising moments the character’s repressed sensuality.

As a “Savoyard” (the appellation to which only those D’Oyly Carte members who performed at the Savoy Theatre are entitled), Patricia Leonard remained true to the standards and qualities required by the company’s unique performance style, which may be summarised as a combination of good taste and good fun. Yet this was a theatrical lifestyle that demanded sacrifices. This was a year-round occupation, with often 47 weeks on tour with a brief summertime period for rehearsals. For the couple a normal home and family life was impossible, and they could usually see their son Andrew only at school holidays. A typical week on tour would comprise eight performances as well as rehearsals, leaving little time for golf, which the couple enjoyed.

Yet when D’Oyly Carte closed in February 1982 it was a bitter blow. There were concert engagements with former D’Oyly Carte colleagues, short tours with other companies such as the newly reformed Carl Rosa, and appearances at the International Gilbert and Sullivan Festival at Buxton, but this was not regular work. For about six years the couple were licensees of public houses at Betley, Staffordshire, and in Henley. Singing was always the prime occupation and Leonard continued singing until she discovered that she had cancer of the throat.

She is survived by her husband and a son.

Patricia Leonard, principal contralto of the D’Oyly Carte opera, was born on March 9, 1936. She died of throat cancer on January 28, 2010, aged 73