बिना तैयारी का  =  extemporaneous
An ad lib performance

यथेच्छ  =  how
He spoke ad lib.

बिना तैयारी के  =  how
He is famous for singing ad lib.

इच्छानुसार  =  how
He spoke ad lib.

तत्काल भाषण देना  =  perform
She often forgot her lines on stage but she was very good at ad libbing.

बिना तैयारी के बोलना  =  perform
She had no time to prepare but she beautifully ad libbed her lines.

बिना तैयारी के ही सुनाना  =  perform
They ad libbed the duet.

बिना तैयारी के देना  =  perform
He ad libbed a speech at the wedding.