could instrument
Regular verb: instrument - instrumented- instrumented

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could instrument
you could instrument
he could instrument
we could instrument
you could instrument
they could instrument 	I could be instrumenting
you could be instrumenting
he could be instrumenting
we could be instrumenting
you could be instrumenting
they could be instrumenting	I could have instrumented
you could have instrumented
he could have instrumented
we could have instrumented
you could have instrumented
they could have instrumented	I could have been instrumenting
you could have been instrumenting
he could have been instrumenting
we could have been instrumenting
you could have been instrumenting
they could have been instrumenting	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't instrument
you couldn't instrument
he couldn't instrument
we couldn't instrument
you couldn't instrument
they couldn't instrument 	I couldn't be instrumenting
you couldn't be instrumenting
he couldn't be instrumenting
we couldn't be instrumenting
you couldn't be instrumenting
they couldn't be instrumenting	I couldn't have instrumented
you couldn't have instrumented
he couldn't have instrumented
we couldn't have instrumented
you couldn't have instrumented
they couldn't have instrumented	I couldn't have been instrumenting
you couldn't have been instrumenting
he couldn't have been instrumenting
we couldn't have been instrumenting
you couldn't have been instrumenting
they couldn't have been instrumenting	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I instrument?
could you instrument?
could he instrument?
could we instrument?
could you instrument?
could they instrument? 	could I be instrumenting?
could you be instrumenting?
could he be instrumenting?
could we be instrumenting?
could you be instrumenting?
could they be instrumenting? 	could I have instrumented?
could you have instrumented?
could he have instrumented?
could we have instrumented?
could you have instrumented?
could they have instrumented? 	could I have been instrumenting?
could you have been instrumenting?
could he have been instrumenting?
could we have been instrumenting?
could you have been instrumenting?
could they have been instrumenting? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I instrument?
couldn't you instrument?
couldn't he instrument?
couldn't we instrument?
couldn't you instrument?
couldn't they instrument? 	couldn't I be instrumenting?
couldn't you be instrumenting?
couldn't he be instrumenting?
couldn't we be instrumenting?
couldn't you be instrumenting?
couldn't they be instrumenting? 	couldn't I have instrumented?
couldn't you have instrumented?
couldn't he have instrumented?
couldn't we have instrumented?
couldn't you have instrumented?
couldn't they have instrumented? 	couldn't I have been instrumenting?
couldn't you have been instrumenting?
couldn't he have been instrumenting?
couldn't we have been instrumenting?
couldn't you have been instrumenting?
couldn't they have been instrumenting?