I were in London in 2003 at the Public Records Office and found that Thomas Ainslie was promoted to Sergeant on 1 October 1834 and came on board the HMS Athol to SA in 1835. The word Band is written in the Remarks column next to his name. A few other members of the Regiment had the same next to their names. One of the officials who helped me was of the opinion this meant that they were members of the Regimental band.
Interesting that you mentioned that his daughter's names was Marta Victoria. According to my records her names were Mary Henderson