Editing Vibraphone (section)

===Resonators===
Resonators are thin-walled tubes, typically made of aluminum, but any suitably strong material can be used. They are open at one end and closed at the other. Each bar is paired with a resonator whose diameter is slightly wider than the width of the bar and whose length to the closure is one-quarter of the wavelength of the fundamental frequency of the bar. When the bar and resonator are properly in tune with each other, the vibrating air beneath the bar travels down the resonator and is reflected from the closure at the bottom, then returns to the top and is reflected back by the bar, over and over, creating a much stronger standing wave and increasing the amplitude of the fundamental frequency.<ref>{{Cite web |last=Stevens |first=Leigh Howard |author-link=Leigh Howard Stevens |date=2019 |title=The Acoustics of Resonators |url=https://malletech.com/wp-content/uploads/2019/01/Acoustics_of_Resonators1-4.pdf |publisher=Malletech |page=12}}</ref> The resonators, besides raising the upper end of the vibraphone's [[Dynamics (music)|dynamic]] range, also affect the overall tone of the vibraphone, since they amplify the fundamental frequency, but not the upper partials.<ref>{{Cite book |last1=Tuttle |first1=B. C. |last2=Burroughs |first2=C. B. |date=1998 |title=The Effects of a Resonator Tube on the Timbre and Directivity of Sound Radiated from a Vibraphone Bar |publisher=[[Pennsylvania State University]] |page=6 |citeseerx=10.1.1.482.5193 |oclc=198987505}}</ref>

There is a trade-off between the amplifying effect of the resonators and the length of sustain of a ringing bar. The energy in a ringing bar comes from the initial mallet strike, and that energy can either be used to make the bar ring louder initially, or not as loudly but for a longer period of time. This is not an issue with marimbas and xylophones, where the natural sustain time of the wooden bars is short, but vibraphone bars can ring for many seconds after being struck, and this effect is highly desirable in many circumstances. Therefore, the resonators in a vibraphone are usually tuned slightly off-pitch to create a balance between loudness and sustain.{{Sfn|Rossing|2000|p=66}}

A unique feature of vibraphone resonators is the shaft of rotating discs, commonly called fans, across the top. When the fans are open, the resonators have full function. When the fans are closed, the resonators are partially occluded, reducing the resonance of the fundamental pitch. A [[Belt (mechanical)|drive belt]] connects the shafts to an electric motor beneath the playing surface and rotates the fans. This rotation of the fans creates a [[tremolo]] effect and a slight [[vibrato]].<ref>{{Cite book |last=Hosken |first=Daniel W. |url=https://www.worldcat.org/oclc/869365321 |title=An Introduction to Music Technology |publisher=[[Taylor & Francis]] |year=2015 |isbn=978-0-415-82572-6 |edition=2nd |location=New York, NY|oclc=869365321 }}</ref>

Oftentimes, vibraphones, and other mallet instruments, will include non-functional, decorative resonator tubes with no corresponding bar above to make the instrument look more complete.<ref>{{Cite web |last=Yamaha |title=The Structure of the Marimba: Inside and outside the resonator pipes |url=https://www.yamaha.com/en/musical_instrument_guide/marimba/mechanism/mechanism002.html |access-date=3 September 2020 |website= |language=en}}</ref>

In 1970, Deagan introduced the ElectraVibe, which dispensed with resonator tubes entirely and took a signal directly from the bars, adding a tremolo in a preamplifier. This sought to improve the portability of the instrument and solve the problem inherent in all tuned mallet instruments: miking the bars evenly.{{Sfn|Beck|2007|p=401}}