Her mother was an amateur singer and pianist who had been unable to pursue her own professional music studies because of politics in Korea during the 1950s.

[6] In 1976, Jo entered the Sun Hwa Arts School from which she graduated in 1980, receiving dual diplomas in voice and piano.

While Jo studied in Italy, she was frequently heard in concert in Italian cities and on national radio broadcasts and telecasts.

It was during this time when Jo began to use "Sumi" as her stage name in order to make her name more friendly to European language speakers who often found it difficult to pronounce Su-gyeong.

[citation needed] Following graduation, Jo began to study with Elisabeth Schwarzkopf[6] and won several international competitions in Seoul, Naples, Enna, Barcelona, and Pretoria.

This performance drew the attention of Herbert von Karajan, who proceeded to cast her as Oscar in Un ballo in maschera opposite Plácido Domingo for the 1989 Salzburg Festival.

[12] That same year she made her debut with the Bavarian State Opera and sang Barbarina in The Marriage of Figaro at the Salzburg Festival.

In 1989, Jo made her debut with the Vienna State Opera and returned to the Salzburg Festival to sing Oscar in Verdi's Un ballo in maschera.

[13] In 1990, Jo made her debut with the Chicago Lyric Opera as the Queen of the Night in Mozart's The Magic Flute.

Over the next decade Jo maintained a busy schedule, singing Lucia in Strasbourg, Barcelona, Berlin, and Paris; La sonnambula in Brussels and Santiago, Chile; I Capuleti e i Montecchi with Minnesota Opera; Olympia and Rosina in New York; the Queen of the Night in Los Angeles; Gilda in Bilbao, Oviedo, Bologna, Trieste, and Detroit among others; Il turco in Italia in Spain; L'enfant et les sortilèges in Boston and Pittsburgh; Le comte Ory in Rome; and Dinorah in New York.

Her work led her to sing under such conductors as Sir Georg Solti, Zubin Mehta, Lorin Maazel, James Levine, Kent Nagano, and Richard Bonynge.

On 9 March 2018, Jo performed a specially-recorded duet with fellow vocalist Sohyang, the song "Here As One", during the opening ceremony of the 2018 Winter Paralympic Games in Pyeongchang, South Korea.

On the red carpet prior to the ceremonies, Jo and Lang voiced their disappointment with the producers' decision to exclude the song, indirectly referencing the controversy related to that year's Academy Awards and its lack of racial diversity.

[25] Aria of Zerbinetta in Ariadne auf Naxos, written by Richard Strauss in 1912, is a difficult piece over 20 minutes in length with numerous high notes.