Given he can play left-back, centre-half or defensive midfield, it was likely Musa would be paired with his former Team Wellington team mate Michael Eagar, now SMFC captain, at centre-half.
The young man has had a good impact, being named man of the match in his club's 1-0 win over Melbourne Knights in their local derby last Sunday, making it seven wins on the trot for South Melbourne 2014.
SMFC's football director Nicholas Maikousis was delighted with the signing.
"It is quite a coup to secure the playing services of James given his experience playing in the A League and the United Kingdom.
"He will join what is looking like a formidable defence at South and look forward to him having a big season."
While the club now plays below A-League, SMFC is considered the most successful soccer club in Australia. Established in 1959, they have won four national championships, a host of Victorian State League titles, and represented Oceania in the 2000 FIFA Club World Championship.