Grammenos' musical intellegence and virtuosity have been recognised  by conductors and instrumentalists worlwide. His international career was launched when he won the first prize at the Eurovision Young Musicians International Competition 2008 (the first wind player to win this competition) performing live, during the Wiener Festwochen's Opening Ceremony, in front of an audience of 50.000. Grammenos has appeared with prestigious Orchestras and Ensembles, such as the Wiener Symphoniker, Sofia Philharmonic Orchestra, Norwegian Radio Orchestra, Qatar Philharmonic Orchestra, Polish Chamber Orchestra, Nordic Chamber Orchestra, State Orchestras of Greece, Berlin Philharmonia Quartet, Swedish Wind Ensemble, and at renown festivals and concert halls, such as the Wiener Festwochen, Rheingau Musik Festival, Auditorium Musée du Louvre, Vienna Konzerthaus, Auditorio Nacional de Musica de Madrid, Minato Mirai Hall, Royal Academy of Arts in London, Athens Concert Hall.  Daniel Stabrawa, first concert master of the Berlin Philharmonic Orchestra, has aslo recognised Grammenos to be a "child prodigy", encouraging him to take up conducting. Grammenos made his conducting debut at the age of twenty-one with the Vienna Chamber Orchestra. Grammenos was appointed Artistic Director of the Corfu Festival of Arts in 2010.