I could tone you could tone he could tone we could tone you could tone they could tone
V-ing form
I could be toning you could be toning he could be toning we could be toning you could be toning they could be toning
Perfect
I could have toned you could have toned he could have toned we could have toned you could have toned they could have toned
V-ing perfect
I could have been toning you could have been toning he could have been toning we could have been toning you could have been toning they could have been toning
Negation
Simple form
I could not tone you could not tone he could not tone we could not tone you could not tone they could not tone
V-ing form
I could not be toning you could not be toning he could not be toning we could not be toning you could not be toning they could not be toning
Perfect
I could not have toned you could not have toned he could not have toned we could not have toned you could not have toned they could not have toned
V-ing perfect
I could not have been toning you could not have been toning he could not have been toning we could not have been toning you could not have been toning they could not have been toning
Interrogative form
Simple form
could I tone? could you tone? could he tone? could we tone? could you tone? could they tone?
V-ing form
could I be toning? could you be toning? could he be toning? could we be toning? could you be toning? could they be toning?
Perfect
could I have toned? could you have toned? could he have toned? could we have toned? could you have toned? could they have toned?
V-ing perfect
could I have been toning? could you have been toning? could he have been toning? could we have been toning? could you have been toning? could they have been toning?
Interro-negative form
Simple form
could I not tone? could you not tone? could he not tone? could we not tone? could you not tone? could they not tone?
V-ing form
could I not be toning? could you not be toning? could he not be toning? could we not be toning? could you not be toning? could they not be toning?
Perfect
could I not have toned? could you not have toned? could he not have toned? could we not have toned? could you not have toned? could they not have toned?
V-ing perfect
could I not have been toning? could you not have been toning? could he not have been toning? could we not have been toning? could you not have been toning? could they not have been toning?