The audition requirements for the band are available on the RNZN website. You will be asked about your career ambitions, especially regarding your intention to commit for a longer period of time. You will be required to demonstrate proficiency on your instrument - think scales, arpeggios, etudes, standards etc. You will be asked about your ability to work in a military environment [re. ranks, orders, basic training etc.], but be aware some of this may be implicit.