im not saying im good at viva voce but to me viva is a more extensive and in depth version of aural, but u do it beforehand.
for eg in aural you talk about tonecolour contrast texture etc about the piece hat ur lsitening to, then you do that same thing for whatever the pieces are for ur viva voce. e.g. im doing a metallica viva for 20th century and my teacher said talk about the different styles, and thought it is ALL metal. you can say how nothing else matter is a ballad introducton while sandman utilises synthenisers and wah wah(even demonstrating if u have a pedal) and master is the full on rock(powerchords talk about repeating riff/theme).
while some people do talk about origins of the piece or whatever, i think for what im doing (20th centruy-metallica) and film music-high school musical, musical elements will suffice. or so my teacher says
she also says to demonstrate. like demonstrate what a hammer on is, what a bend is, demonstrate the chord progression used. (e.g. in nothing else matter the intro is a appregiated Em(i),Am(iv), C(vi) and d(vii), you could paly the excerpt once, talk about it whatever then splay it again while playing the chord progression and say its interetsing to note the chord progression as the C chord later turns into a Cadd2...blah blah
well thats how i see it...
hope i helped.
