Amplifying sound
Well, it’s about physics. However, what I know about physics is dangerous and so I am going to explain resonators in my own layman’s words. Every instrument makes sound that is amplified in some way or other. A guitar has a string which is plucked or strummed, and the body of the guitar amplifies that sound – we might struggle to hear the string being plucked without the resonating space provided by the guitar. Think about how your voice can sound very loud if you’re in an empty bathroom, or a big empty hall.
Amplifying wood’s sound
So the marimba note, or ‘key’ – made of a slab of wood – it struck by a mallet, and to make it louder, there is some sort of resonating space. Marimbas made in South Africa have different kinds of resonators. Resonance either happens because of reflection (like when you sing in the shower, the sound is bouncing off the walls of the shower and making you sound really good). Or resonance happens because the resonating space matches the pitch of the note. The marimbas made in South Africa usually use one or the other of these systems. Some, like Marimba Workshop’s soprano instruments, use reflection. As you will see in the main pic, half of the Marimba Workshop tenor/bass marimba has no individual resonators for the notes, but a long trough beneath the keyboard. The lower half does have separate resonators for each note. What tends to result when several notes share a resonating space is an uneven tone across the keyboard, with some notes sounding louder and others being much weaker. Some makers produce marimbas which have a separate resonator for every two notes. This gives more resonance than the reflection method, but the resonators cannot be perfectly tuned to any one particular note. The AMI instruments only use the trough system for piccolo instruments. AMI soprano, tenor, baritone and contrabass marimbas all have separate resonators that are each tuned perfectly to their respective notes. AMI produce marimbas with pipe resonators – made with plastic piping – and marimbas with wooden resonators. The pipe resonators (pictured below) produce a sound that is softer, but also lighter in weight. So they’re a bit easier to move around. The pipes are safely clad in a plywood casing, so they are protected from damage, and they look sleek. The wooden resonators produce a more powerful sound than the pipe resonators. If it’s volume you are after – these are what you need. They are heavier to move around and a bit more expensive, but the sound is fantastic. So think about this if you are buying instruments – the resonating options do make a difference.
Choice of wood
While on the subject of resonance – sound starts with the vibration of the wooden notes of the marimba or xylophone. And what is crucial here is the kind of wood that is used. Some woods are far more resonant than others and this has to do with a few different factors. Kiaat (Pterocarpus angolensis) is used for most South African marimbas although pedauk (Pterocarpus soyauxii) is also used by some makers. Both of these woods are richly resonant – they are known as ‘tone woods’. Surpassing both of these in tone is sneezewood (Ptaeroxylon obliquum). AMI’s supply of sneezewood comes from 100-year-old fence posts from Eastern Cape farms. The wood is very dense, very heavy, emits a very strong dust when cut which makes you sneeze (or gives you an allergic reaction), and has an exquisite golden colour. To ramp up the tone even more, the notes cut from sneezewood can be tempered in an oven or fire. This is a tip learned from the Chopi xylophone makers in Mozambique. Once tempered, sneezewood notes do not go out of tune. They have a brilliant and strident tone. We take advantage of this by using tempered sneezewood for AMI Orff xylophones and for the AMI log xylophones. AMI log xylophones don’t have any resonators, but rely on the resonance of the wood itself – either kiaat, or sneezewood.
