A pit-house was formed by first digging a room in the ground. The next step was to add a roof, typically with wood. Another name for a pit-house is sunken featured buildings.
A good performance flute will be fine. "Pit orchestra" simply means the orchestra is located in a sunken area in front of a stage, called the "pit." There are no particular instruments for a pit orchestra, nor is there any particular size of orchestra that plays in a pit.
The "pit" is an area just in front of the stage itself. It may be sunken below the rest of the floor. For musicals, it's usually used for the orchestra, but for conventional plays where there's no orchestra, it can be used for seating.
Sunken is not a verb so it doesn't have present or past tense. Sunken is an adjective
generally xerophytic plants have sunken stomata
The Sunken World was created in 1948.
The Sunken Billions was created in 2008.
The Sunken Cemetery was created in 2002.
the opposite of sunken area is inlet
Sunken Treasures was created in 1993.
The Sunken Threshold was created in 2006-02.
Dehidration is a major cause in sunken veins.