Dear Joe
If this is inappropriate, I apologise. Please advise, & I will do what is necessary in order to post my query.

I have posted this query on a variety of places like reddit & Facebook, but have yet to have it answered. This is frustrating because I do know that there is a specific musical term/direction for this deliberate & distinctive effect.

What I would like to know is the correct musical term for when two voices go against their usual/expected relationship to each other; defying their expected range/pitch relationship? It is likely that this is seen involving more than two voices, but I am unaware of that.
The two (or more voices) continue singing in their 'normal' range, but they both/all become 'inverted' ( 'inverted' is unlikely to be a correct term) i.e. the soprano is now singing a 'lower' pitch than the bass & the bass is now pitched 'higher' than the soprano?

Purely as a means of simplifying for clarity, I am assigning gender to the voices & apologise if this causes any offence. So: the top voice is to be female; the lower voice to be male.

If so, then the soprano voice is now singing a 'lower' part than the bass?

They have not 'switched' parts & begun singing the other person's line; they both continue, completely normally, singing 'their' line, and very simply, their line has taken them above or below the other's pitch?


It does not require any special techniques nor changing of vocal style: both voices continue as 'normal' but their individual voices are not; the bass's pitch is now higher than the sopranos & similarly: the soprano's pitch is now lower than the bass's

A fairly well-known example of this in a popular song is: 'Somethin' Stupid' (sic) by Frank & Nancy Sinatra.

Thank you,

https://www.youtube.com/watch?v=Y_t2gNCXYbY