In 1944, Jaan Hargel was invited to play in the orchestra of the Vanemuine Theatre where, in the difficult post-war years, he could soon try his hand at conducting. His debut as a conductor was in 1944 with August Kitzberg's drama Before Cock's Crow with incidental music by Richard Ritsing. This was soon followed by Leo Fall's operetta Der fidele Bauer and the first opera – Eugen Kapp's Flames of Revenge. Conducting at the Vanemuine became Jaan Hargel's life's work – 22 years in total, including six seasons as the principal conductor of the theatre. More than 70 operas, ballets and operettas were staged at the Vanemuine under Jaan Hargel's conduction. His role at staging original works of Estonian music needs particular emphasis. He conducted the first productions of the first Soviet Estonian operetta, Edgar Arro and Leo Normet's Rummu Jüri, Boris Kõrver's operetta Just a Dream and Gustav Ernesaks' opera Suitors from Mulgimaa, which was played more than 130 times. Evald Aav's opera Vikings acquired particular significance for him. It was staged at the Vanemuine in 1955 with an orchestration renewed by him. Four years later, under his conduction, it became the first opera that was recorded in full in Estonia. Jaan Hargel orchestrated Gustav Ernesaks' opera Suitors from Mulgimaa and participated in making the new versions of Ernesaks' operas Baptism of Fire and Hand in Hand. The latter, conducted by Jaan Hargel, also completed the 1965 Song Festival in Tallinn as an open-air performance. A lot of positive feedback was given to Jaan Hargel's conduction of Rossini's opera Il barbiere di Siviglia, Mozart's Die Zauberflöte, Leoncavallo's I pagliacci, Tchaikovsky's Iolanta, Verdi's Aida, d'Albert's Tiefland, and a number of extremely popular operettas, e.g. Strauss' Die Fledermaus, Hervé's Mam'zelle Nitouche, Raymond's Maske in Blau, Kitzberg's farce with Eduard Oja's music Taylor Õhk andHis Winning Lottery Ticket, which in Hargel's lifetime was played for almost 140 times, and one of the most successful ballet productions of the Vanemuine throughout the times – Peer Gynt to Grieg's music. Jaan Hargel's last production at the Vanemuine was Nicolai's opera Die lustige Weiber von Windsor, which he could conduct for only a few times before his early death. In addition to theatre music, Jaan Hargel conducted symphony concerts and, if necessary, performed as a flute player under other conductors at symphony concerts or substituting for orchestra members who had fallen ill.
Career as a teacher
Along with being a conductor and instrumentalist, he also worked as a music teacher until the end of his life. From 1940–44, he worked as an oboe teacher at Tallinn Conservatoire where his best-known student was Herman Talmre, the long-time principal oboist with the Estonian Radio Symphony Orchestra. From 1946–49, he taught at Tartu Teacher Training Institute and from 1948–66 at Tartu Music School where his students were Heldur Värv, Alo Põldmäe, Jaan Õun, Peeter Rööp, Ilmar Aasmets, etc.
Personal
Jaan Hargel's father Jaan Hargel, afterwards changed his name to Hargla, was an actor at Tallinn Drama Theatre, ballroom dancing instructor, football and athletics referee; his wife Alvi Hargel, up to 1947 Tilk, was a singer at the Vanemuine Theatre; his son Jaan Hargel was an interior architect; his son Jüri Hargel is a flautist and flute teacher.