Portamento can make the vocal music of the flute more gorgeous, smooth and colorful. There are two kinds of portamento, "finger portamento" and "air portamento".
Finger portamento is a portamento effect produced by gradually pressing or gradually opening the finger on the sound hole.
The portamento is a portamento effect produced by the control of breath, such as the strength, rapidity, and change of the size and position of the air door.
When playing portamento, these two portamento methods are generally combined with each other, that is, when the finger is gradually pressed or gradually opened, it is combined with the control of the breath and the movement of the damper position to create a portamento effect.
In a piece of music, sliding up from a lower note to another note is called "glide down"; from a higher note down to another note, it is called "glide".