Bending tempo with irregular metre

It took me a long time into my musical development to understand that bending of tempo was OK – and that it happens everywhere. Almost no music goes at a metronomic tempo throughout, only as I used to think being adjusted for concluding rits or expressly indicated moments of rubato (or allargando, accelerando, stringendo etc).

No, tempo bends all the time – most bars. Particularly choral music where breaths are required, and robbing note lengths in order to breathe would sound very

No, in real music time is added all over the place, and the metronome gets its P45.

Take for example the opening line of one of Epiphoni’s¬†favourites pieces of the moment Never Weather Beaten Sail:

 

 

But I’m in a quandary as what to do in piece of irregular metre such as Gabriel Jackson’s Song (I Gaze Upon You), which we’re performing on 9th May.

If you bend tempo on 5/8 and 3/8 bars don’t the just become 3/4 and 2/4? Does this defeat the purpose?