must harken
Regular verb: harken - harkened- harkened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must harken
you must harken
he must harken
we must harken
you must harken
they must harken 	I must be harkening
you must be harkening
he must be harkening
we must be harkening
you must be harkening
they must be harkening	I must have harkened
you must have harkened
he must have harkened
we must have harkened
you must have harkened
they must have harkened	I must have been harkening
you must have been harkening
he must have been harkening
we must have been harkening
you must have been harkening
they must have been harkening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't harken
you mustn't harken
he mustn't harken
we mustn't harken
you mustn't harken
they mustn't harken 	I mustn't be harkening
you mustn't be harkening
he mustn't be harkening
we mustn't be harkening
you mustn't be harkening
they mustn't be harkening	I mustn't have harkened
you mustn't have harkened
he mustn't have harkened
we mustn't have harkened
you mustn't have harkened
they mustn't have harkened	I mustn't have been harkening
you mustn't have been harkening
he mustn't have been harkening
we mustn't have been harkening
you mustn't have been harkening
they mustn't have been harkening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I harken?
must you harken?
must he harken?
must we harken?
must you harken?
must they harken? 	must I be harkening?
must you be harkening?
must he be harkening?
must we be harkening?
must you be harkening?
must they be harkening? 	must I have harkened?
must you have harkened?
must he have harkened?
must we have harkened?
must you have harkened?
must they have harkened? 	must I have been harkening?
must you have been harkening?
must he have been harkening?
must we have been harkening?
must you have been harkening?
must they have been harkening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I harken?
mustn't you harken?
mustn't he harken?
mustn't we harken?
mustn't you harken?
mustn't they harken? 	mustn't I be harkening?
mustn't you be harkening?
mustn't he be harkening?
mustn't we be harkening?
mustn't you be harkening?
mustn't they be harkening? 	mustn't I have harkened?
mustn't you have harkened?
mustn't he have harkened?
mustn't we have harkened?
mustn't you have harkened?
mustn't they have harkened? 	mustn't I have been harkening?
mustn't you have been harkening?
mustn't he have been harkening?
mustn't we have been harkening?
mustn't you have been harkening?
mustn't they have been harkening?