The following chart shows how the recorder plays high notes.
Velocity antinodes (A) are low pressure zones with high speed or movement. Velocity nodes (N), on the contrary are high pressure zones with no
speed or movement. If the bell is open there is always an antinode at each end.
Waves that travel along the bore of the instrument meet at the nodes and continue until they reach the opposite end of the tube where they bounce back, and keep on moving up and down in this way in this way as long as the player keeps blowing.
This note belongs to the fourth register. The leaking thumb hole, combined with two other open holes in the correct places inhibits the nodes of the first three registers and thus causes the air column to divide into four parts.. There are four nodes here.
Not only do the vibrations go up and down from the ends of the air column to the nodes, but also
between the nodes, with maximum velocity at the antinodes.
The chart shows the position of the nodes and antinodes. There is one graph for velocity and one for pressure variations along the air column.
The arrows show the direction of the vibrations.
The recorder's bore profile, and the open (o), closed (x),and partially closed (ø) holes are shown underneath.
In the high registers the air column uses the whole length of the instrument's bore.
The nodes and antinodes described here are velocity nodes and antinodes.