could modulate
Regular verb: modulate - modulated- modulated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could modulate
you could modulate
he could modulate
we could modulate
you could modulate
they could modulate 	I could be modulating
you could be modulating
he could be modulating
we could be modulating
you could be modulating
they could be modulating	I could have modulated
you could have modulated
he could have modulated
we could have modulated
you could have modulated
they could have modulated	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 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't modulate
you couldn't modulate
he couldn't modulate
we couldn't modulate
you couldn't modulate
they couldn't modulate 	I couldn't be modulating
you couldn't be modulating
he couldn't be modulating
we couldn't be modulating
you couldn't be modulating
they couldn't be modulating	I couldn't have modulated
you couldn't have modulated
he couldn't have modulated
we couldn't have modulated
you couldn't have modulated
they couldn't have modulated	I couldn't have been modulating
you couldn't have been modulating
he couldn't have been modulating
we couldn't have been modulating
you couldn't have been modulating
they couldn't have been modulating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I modulate?
could you modulate?
could he modulate?
could we modulate?
could you modulate?
could they modulate? 	could I be modulating?
could you be modulating?
could he be modulating?
could we be modulating?
could you be modulating?
could they be modulating? 	could I have modulated?
could you have modulated?
could he have modulated?
could we have modulated?
could you have modulated?
could they have modulated? 	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 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I modulate?
couldn't you modulate?
couldn't he modulate?
couldn't we modulate?
couldn't you modulate?
couldn't they modulate? 	couldn't I be modulating?
couldn't you be modulating?
couldn't he be modulating?
couldn't we be modulating?
couldn't you be modulating?
couldn't they be modulating? 	couldn't I have modulated?
couldn't you have modulated?
couldn't he have modulated?
couldn't we have modulated?
couldn't you have modulated?
couldn't they have modulated? 	couldn't I have been modulating?
couldn't you have been modulating?
couldn't he have been modulating?
couldn't we have been modulating?
couldn't you have been modulating?
couldn't they have been modulating?