Mackenzie was regarded as a cosmopolitan musician. He spoke fluent German and Italian and was elected to the post of President of the International Musical Society which he held from 1908 to 1912. From his early days playing in orchestras in Edinburgh and Birmingham he had met and become friendly with many leading international musicians, including Clara Schumann, Joseph Joachim, Charles Gounod and Antonín Dvořák. His friendship with Liszt began in Mackenzie's student days in Sondershausen and lasted for the rest of Liszt's life.