Open to anyone who wants to work with the course leader or within the theme of that particular course. Content and repertoire will reflect a wide variety and you should feel confident to tackle some of the repertoire suggested at whatever level you are currently working. The course leader will adapt their advice and teaching on an individual basis.
You may have had some individual tuition at some point in your life and want to refresh this. You may be moving on to the next stage, e.g. thinking about having regular lessons or playing/singing in a more formal ensemble on a more regular basis; perhaps you are working towards a grade exam or performance in some capacity. You can probably read some music.
For people who have perhaps a little limited experience of the voice or relevant instrument, perhaps they have sung/do sing in a choir or played an instrument at school. You may not be able to read music and do not need to have had any formal training at all, or may have forgotten any formal training they have had and want to get started again.
You have had some individual tuition with a teacher and play your instrument regularly or sing regularly and probably solo. You may be working towards an advanced grade exam or diploma or be a current or recently graduated music student. You may be a more seasoned performer who wants to work on a specific area or work in ensembles.