After her army service in the Israeli Air Force, she studied at the Beit Zvi Academy of Performing Arts in Ramat Gan, specializing in musical theatre with Dorit Atzmon.
As part of her studies she appeared, among others, as Polly Peachum in the musical The Threepenny Opera by Bertolt Brecht and Kurt Weill, as Eliza Doolittle in My Fair Lady by Alan Jay Lerner and Frederick Loewe and as the High Priestess in Hair by James Rado, Gerome Ragni and Galt MacDermot.
During this time Keren met her life-partner, Alon Reuven, Principal Horn of the Israel Camerata Jerusalem, and through his encouragement returned to her classical voice training with soprano Sharon Rostorf-Zamir and Efrat Ben-Nun.
She also took classes in the Musicology Department and the Music Academy at Tel Aviv University, including harmony, sight-reading and diction in various languages, in addition to German studies at the Goethe Institute in Tel-Aviv.
Hadar made numerous appearances with the pianist and conductor Yoni Farhi, the horn player Alon Reuven and the classical guitarist Daniel Akiva in Israel and abroad, including England, Germany, China, Croatia, Belgium and Poland.