I would like to use auxiliary notes with techniques other than trill. For example, non-unison simultaneous playing and singing may be notated with the played note as an ordinary note, and the sung note as an auxiliary note, inside cautionary parentheses (please see attached example).
How would you notate it? I’m thinking to a second voice, with offset position. This would also allow for two different timbres. But I wonder if there is different way to do it.