I could improvise you could improvise he could improvise we could improvise you could improvise they could improvise
V-ing form
I could be improvising you could be improvising he could be improvising we could be improvising you could be improvising they could be improvising
Perfect
I could have improvised you could have improvised he could have improvised we could have improvised you could have improvised they could have improvised
V-ing perfect
I could have been improvising you could have been improvising he could have been improvising we could have been improvising you could have been improvising they could have been improvising
Negation
Simple form
I couldn't improvise you couldn't improvise he couldn't improvise we couldn't improvise you couldn't improvise they couldn't improvise
V-ing form
I couldn't be improvising you couldn't be improvising he couldn't be improvising we couldn't be improvising you couldn't be improvising they couldn't be improvising
Perfect
I couldn't have improvised you couldn't have improvised he couldn't have improvised we couldn't have improvised you couldn't have improvised they couldn't have improvised
V-ing perfect
I couldn't have been improvising you couldn't have been improvising he couldn't have been improvising we couldn't have been improvising you couldn't have been improvising they couldn't have been improvising
Interrogative form
Simple form
could I improvise? could you improvise? could he improvise? could we improvise? could you improvise? could they improvise?
V-ing form
could I be improvising? could you be improvising? could he be improvising? could we be improvising? could you be improvising? could they be improvising?
Perfect
could I have improvised? could you have improvised? could he have improvised? could we have improvised? could you have improvised? could they have improvised?
V-ing perfect
could I have been improvising? could you have been improvising? could he have been improvising? could we have been improvising? could you have been improvising? could they have been improvising?
Interro-negative form
Simple form
couldn't I improvise? couldn't you improvise? couldn't he improvise? couldn't we improvise? couldn't you improvise? couldn't they improvise?
V-ing form
couldn't I be improvising? couldn't you be improvising? couldn't he be improvising? couldn't we be improvising? couldn't you be improvising? couldn't they be improvising?
Perfect
couldn't I have improvised? couldn't you have improvised? couldn't he have improvised? couldn't we have improvised? couldn't you have improvised? couldn't they have improvised?
V-ing perfect
couldn't I have been improvising? couldn't you have been improvising? couldn't he have been improvising? couldn't we have been improvising? couldn't you have been improvising? couldn't they have been improvising?