Answer: rectative, aria, ground bass and triple. 
Explanation:
The rhythm of the RECITATIVE is free, and the rhythm of the ARIA is more regular. The harmony of the aria is based on a chromatic GROUND BASS that descends by half step. The slow and melancholy TRIPLE meter expresses in the aria Dido's lamentation at Aeneas's departure. 
 
        
                    
             
        
        
        
In music theory<span>, a </span>scale<span> is any set of musical </span>notes<span> ordered by </span>fundamental frequency<span> or </span>pitch<span>. A scale ordered by increasing pitch is an ascending scale, and a scale ordered by decreasing pitch is a descending scale. Some scales contain different pitches when ascending than when descending, for example, the </span>melodic minor scale<span>.</span>