I could modulate you could modulate he could modulate we could modulate you could modulate they could modulate
V-ing form
I could be modulating you could be modulating he could be modulating we could be modulating you could be modulating they could be modulating
Perfect
I could have modulated you could have modulated he could have modulated we could have modulated you could have modulated they could have modulated
V-ing perfect
I could have been modulating you could have been modulating he could have been modulating we could have been modulating you could have been modulating they could have been modulating
Negation
Simple form
I could not modulate you could not modulate he could not modulate we could not modulate you could not modulate they could not modulate
V-ing form
I could not be modulating you could not be modulating he could not be modulating we could not be modulating you could not be modulating they could not be modulating
Perfect
I could not have modulated you could not have modulated he could not have modulated we could not have modulated you could not have modulated they could not have modulated
V-ing perfect
I could not have been modulating you could not have been modulating he could not have been modulating we could not have been modulating you could not have been modulating they could not have been modulating
Interrogative form
Simple form
could I modulate? could you modulate? could he modulate? could we modulate? could you modulate? could they modulate?
V-ing form
could I be modulating? could you be modulating? could he be modulating? could we be modulating? could you be modulating? could they be modulating?
Perfect
could I have modulated? could you have modulated? could he have modulated? could we have modulated? could you have modulated? could they have modulated?
V-ing perfect
could I have been modulating? could you have been modulating? could he have been modulating? could we have been modulating? could you have been modulating? could they have been modulating?
Interro-negative form
Simple form
could I not modulate? could you not modulate? could he not modulate? could we not modulate? could you not modulate? could they not modulate?
V-ing form
could I not be modulating? could you not be modulating? could he not be modulating? could we not be modulating? could you not be modulating? could they not be modulating?
Perfect
could I not have modulated? could you not have modulated? could he not have modulated? could we not have modulated? could you not have modulated? could they not have modulated?
V-ing perfect
could I not have been modulating? could you not have been modulating? could he not have been modulating? could we not have been modulating? could you not have been modulating? could they not have been modulating?