On your Marimba Instrument making and tuning each bar carefully determines the final sound of a musical instrument, regardless of the material being solid wood; though solid wood appears rigid, its vibrational frequencies allow different tones and sounds to come through.
Once again, when building a marimba frame there are only a few rules you should abide by; everything else is left up to you!
Material Selection: A Step in Marimba Construction
Assembling a marimba begins with gathering the necessary materials. You'll require well-seasoned, resonant hardwood for keys, while commercial marimbas typically contain 61 keys that range in length from 7.2 to 21.7 inches and width between 1.6 and 2.9 inches - raised slightly above higher diatonic notes to minimize string vibration effects on tone quality.
Dimensions for bars and resonators vary between instruments, with five-octave sets becoming the industry standard among professional musicians and schools. The material used for the bars also affects sound quality; traditionally rosewood was preferred due to its dense density and resonant qualities; however, due to it becoming harder to obtain alternatives like paduk and babinga have become more commonly used for their bars.
Resonator tubes may be relatively straightforward to produce, but their support frame requires much more intricate planning and implementation. While this challenge may appear insurmountable, with careful thought it can be achieved.
A marimba frame may be constructed out of wood or metal, with wood producing warmer tones while metal produces colder sounds.
As part of building a frame, it is vital to take time to lay out all your keys and resonator tubes in an organized manner. This will allow you to determine the dimensions of the frame as well as where string supports should be located. Marking node positions of bars (the points where they vibrate least when struck) also proves helpful for finding nodes on resonator tubes before cutting them, so as to ensure proper fitting that won't alter their tone or affect the overall tone quality of the instrument.
Building Resonators: Creating Harmonic Tubes
Marimba instruments include more than just bars; they often also feature box or pipe-resonated resonators made of wood such as rosewood or padauk (Diospyros maingayi), plastic or fiberglass materials may also be employed for their construction. Resonators allow the bars to vibrate freely while producing fuller sound quality; additionally, they have an impactful influence on its tone by changing the natural harmonics produced by bars.
Fundamentally, harmonic tubes operate very simply. Energy transfers continuously along their length. This generates pressure waves moving at sound speed that eventually form nodes and antinodes; the relative strength of partials created, known as their "timbre," determines what sounds come out.
To produce a specific note with a bar resonator, its pitch must be altered accordingly. This can be accomplished through grinding on either end or taking small cuts out of material from within it - depending on your frequency goals, this could sharpen or flatten its pitch accordingly.
Resonators play a key role in creating the sound of each bar, so selecting an ideal type for your project is paramount. Most often aluminum or brass tubes will do, though other options exist such as rocketScientist's hollowed-out log resonators which produced excellent sounds!
Resonators used in other instruments include natural gourds, wooden resonators, and, more recently, PVC tubing. Sometimes holes are drilled in the bottom of these tubing tubes so that a membrane made from pig intestines is placed over it, adding its characteristic buzzing noise called "charleo." This gives each instrument its own distinct sound.
Crafting the Keyboard: Marimba Playing Surface
Assuming you have created individual keys (or bars) for your marimba, the next step should be linking them together. This requires highly skilled work as you will need to cut each key underside into an arch shape - which may present quite a challenge! For this step to succeed successfully, each note on your template should be measured carefully to achieve this result; using a circular saw for proforma keys cutting makes precise measurements much simpler, helping avoid warping or warping from occurring and keeps wood from warping or warping during the cutting process.
Use your template as a guide and mark the node position lines on each bar using your node template as a guide. These nodes represent where a bar will resonate when struck, for a five-octave marimba this should be 22.5% from either end of each bar; doing this will ensure optimal sound quality when creating your instrument.
On the underside of each bar is a hole that needs to be connected to all other bars by passing a cord through it. This cord must be long enough to pass through all upper drilled holes on each key and lower drilled holes on all keys so that notes are strung together; an average 5-octave marimba requires 40 feet of bar cord for strumming together all notes.
Once all the bars have been connected, it's advisable to construct resonators for each one. These may be made out of aluminum tubes like those commonly found in concert marimbas or can be constructed out of wood - either way, they add greater vibrancy and clarity when played.
Finally, a frame must be created to hold all of the resonators securely in place. Primitive marimbas often feature an unsophisticated frame like that found on a small table while concert marimbas often resemble trolleys with wheels and have larger frames with hooks or posts to wind the cord around easily.
Assembly and Fine-Tuning: Marimba to Life
Although you might not be able to match the sound produced by marimbas made from rosewood or paduk woods exactly, and their final sound will depend on your care and precision when building and tuning bars, creating professional-sounding instruments using standard materials is absolutely possible and at a much-reduced cost than purchasing them directly from manufacturers.
Once your frame is complete, it's time to assemble and tune your bar assembly to your preference. Use your tuning jig (which should come included with your building guide) to locate each bar's nodes - the points where striking causes minimal vibration - in order to find them all and fine-tune each one for an appealing sound and pleasing tone.
Once the tone of each bar has been determined, it is time to place them on their respective resonator tubes. These tubes can be found at the back of your marimba under its tone plates. Each resonator tube features hollow tubing that extends a certain distance before being closed off at its final length for optimal resonance with each bar on your marimba. In order to get maximum use from your instrument it is imperative that all resonator tubes use similar pitches as the bars found on it.
Before attaching the bars back onto the resonators, take time to inspect each bar for signs of damage and wear. If any exhibit signs of wear and tear, replace them immediately with new sets. It may also be beneficial to cover your marimba when not being used to avoid debris falling into its resonator tubes and damaging it further.
Be mindful when handling and treating a marimba instrument made from wood; they can be delicate. Make sure to cover it when not being played to protect it from dust and moisture damage.