All of the answers I've found so far - here and elsewhere - involve creating a (custom) post - which would be 'overkill' because in this instance many of the 'terms' would only appear once.
Specific example to explain what I'm trying to accomplish:
Person A may be the composer of Song 1; Person A may be the lyricist of Song 2; Person A may be both the composer and lyricist of Song 3; Person A may have been the presenter of Show 1.
I (think I!) want to have one taxonomy of 'person' (i.e. so that Person A is only entered once) with other taxonomies of 'composer', 'lyricist' and 'presenter'. Then on the actual post for Song 1, Song 2, Show 1, etc. I have each person:relationship. A search for Person A would then show that (s)he is connected to:
Song 1, as 'composer'; Song 2, as 'lyricist'; Song 3, as 'composer' and as 'lyricist'; Show 1, as 'presenter'.
Alternatively, if I'm asking the impossible and have to relate through a 'person' custom post, is there an 'easy' (i.e. automatic) way to create it, i.e. when I'm inputting data for a song, show, etc. and just want to enter a name?
Should add that "No ... looked for ages (or tried clever ways) but haven't found a solution" is an acceptable answer. Not the one I was hoping for but at least it might convince me to stop looking / trying!