The vibraphone is a unique mallet instrument in that it is possible to play harmonics. While this can be used to effectively extend the range of the instrument, it becomes increasingly difficult and eventually impossible to activate a harmonic. The bottom few notes can safely be assumed to sound, but going above middle C is risky. Playing in the octave above middle C essentially guarantees no results. This begs the question, why use harmonics at all? In short, the sound simply has a different, perhaps more shimmery sound than if the sounding pitch were played in a normal way.
A harmonic is activated by placing something (ideally a finger) lightly in the exact center of the bar, and then bowing it or striking at the nodal point (where the string runs through the bar). Fingers are preferred over, say, mallets, as it is much easier to find the exact spot needed to activate the harmonic. Regardless of what is used, harmonics have a very low dynamic ceiling.
Unlike instruments that activate harmonics via touching different parts of a string, the vibraphone offers only one result: a sounding pitch two octaves above what is being played. Because of this, it is my personal belief that it’s unnecessary to notate what the sounding pitch is, instead simply indicating harmonics with an “o” above the note in question, as seen in the example below:
In this case, it is implied that the note should be struck. There is nothing wrong with this technique, though I admit I’m not particularly fond of it. Even when done perfectly, the note will sound with the clunky sound of striking a muted bar before the harmonic is clearly heard.
Bowed harmonics are not notated any differently, except of course that some sort of arco notation should be provided. Additionally, the bow allows for a more clear sound of the harmonic, unhindered by the sound of a mallet. When bowed, the harmonic may be activated midway, allowing a seamless transition between the notes, which can be indicated simply by providing the “o” symbol at the desired time.
Generally, playing harmonics requires two hands, so one person would not be able to activate more than one harmonic at a time. Christopher Deane’s The Apocryphal Still-Life requires the performer to play consecutive harmonics with one hand, by holding two mallets in one hand, muting the bar with one mallet and striking the node with the other. It’s an uncomfortable passage, and the dynamic ceiling is particularly low for the actual sounding pitch.
Video coming soon, as soon as it’s safe to venture to my rehearsal space. In the meantime, check out this handy article that provides a few sound samples