English verb conjugation
COULD RIFF

Regular verb: riff - riffed - riffed

Affirmation

Simple form	V-ing form
I could riff you could riff he could riff we could riff you could riff they could riff	I could be riffing you could be riffing he could be riffing we could be riffing you could be riffing they could be riffing
Perfect	V-ing perfect
I could have riffed you could have riffed he could have riffed we could have riffed you could have riffed they could have riffed	I could have been riffing you could have been riffing he could have been riffing we could have been riffing you could have been riffing they could have been riffing

Negation

Simple form	V-ing form
I could not riff you could not riff he could not riff we could not riff you could not riff they could not riff	I could not be riffing you could not be riffing he could not be riffing we could not be riffing you could not be riffing they could not be riffing
Perfect	V-ing perfect
I could not have riffed you could not have riffed he could not have riffed we could not have riffed you could not have riffed they could not have riffed	I could not have been riffing you could not have been riffing he could not have been riffing we could not have been riffing you could not have been riffing they could not have been riffing

Interrogative form

Simple form	V-ing form
could I riff? could you riff? could he riff? could we riff? could you riff? could they riff?	could I be riffing? could you be riffing? could he be riffing? could we be riffing? could you be riffing? could they be riffing?
Perfect	V-ing perfect
could I have riffed? could you have riffed? could he have riffed? could we have riffed? could you have riffed? could they have riffed?	could I have been riffing? could you have been riffing? could he have been riffing? could we have been riffing? could you have been riffing? could they have been riffing?

Interro-negative form

Simple form	V-ing form
could I not riff? could you not riff? could he not riff? could we not riff? could you not riff? could they not riff?	could I not be riffing? could you not be riffing? could he not be riffing? could we not be riffing? could you not be riffing? could they not be riffing?
Perfect	V-ing perfect
could I not have riffed? could you not have riffed? could he not have riffed? could we not have riffed? could you not have riffed? could they not have riffed?	could I not have been riffing? could you not have been riffing? could he not have been riffing? could we not have been riffing? could you not have been riffing? could they not have been riffing?