Is there, I wonder, any sort of rule for how much a fermata should slow a piece of music, i.e. a multiplier of the note duration over which the fermata is placed?
I am trying to realise an accompaniment track for my wife, an operatic mezzo, of the third aria from the Bach Cantata No.82, "Schlummert ein, ihr matten Augen fallet sanft und selig zu." I've transcribed the vocal line up an octave for her.
However the original http://petrucci.mus.auth.gr/imglnks/...38-BWV0082.pdf, see page 37 to 42, has many fermatas (fermati?) in measures 20, 25, 36, 58, 64 and the repeat.
When entering tempo changes into DAW software to implement these, I'm never quite sure what to put, that is by how much should I cut the tempo? Should there be a slight slow down in tempo before the fermata, etc.? I've done some trial and error in previous realisations of fermata but never been completely convinced with the results.
I should be very interested if anyone could give me any pointers.