[1] He was classified as Coloured under apartheid,[2] and he attended the University of the Western Cape, where he completed a Dipl-Juris in 1985, a BA in law in 1988, an LLB in 1991, and an Hons in public administration in 1993.
[1][3] On 31 May 2005, President Thabo Mbeki announced that Musi would join the High Court permanently as a judge of the Free State Division.
[6][7] In April 2014, Musi was among six candidates whom the Judicial Service Commission shortlisted and interviewed for possible permanent appointment to the Labour Appeal Court.
[9] In October 2016, the Judicial Service Commission recommended Musi for appointment as Deputy Judge President of the Free State Division.
[1] At that time, Musi had already served as acting Judge President for brief periods in 2015 and 2016, and in subsequent years, he filled the role on several occasions, filling in for Judge President Mahube Molemela between January and September 2017 and then, after Molemela was elevated to the Supreme Court of Appeal, between June and November 2018.
[1] During the latter period, in August 2018, Musi was the sole candidate whom the Judicial Service Commission shortlisted for possible appointment to succeed Molemela permanently.
[1] In October 2014, President Zuma appointed Musi to succeed Willie Seriti as chairperson of the Independent Commission for the Remuneration of Public Office Bearers.
[17][18] Musi is an active member in the International Association of Judges; from 2010 to 2018, he served as president of its Africa region and a vice-president of the global organisation.