The term xylophonic sounds is a term coined by Carlos Salzedo and is a common used technique.
A xylophonic sound is created by placing a finger on the base of a string and while keeping the finger firm in that position, playing the string.
Usually the left hand is “muffling” the string and the right hand is playing. In this way up to four-five notes can be played at the same time.
This technique can also be performed by using one hand: in this case, a finger is placed at the base of the string and the note is played by the thumb.

The dynamic goes from p to f and is more effective in the middle range. In the higher register it is more percussive and less hearable, in the lower register it will be difficult to perform and also less audible.