Saturday, February 12, 2011
In this post, I will be talking about what to look for when buying a piano. The most important things to consider is the piano's internal construction like the frame, the backposts, soundboard, ribs, bridge, tuning pins and pinblock, actions, hammers, strings, agraffe, pedals and trapwork, and its transition points.
Frame - the frame is the backbone of the piano and it should be heavy so it can resist the strings’ tension and prevent warping. It should be made of cast-iron. The strength of the back and frame directly affects the tuning stability of the piano.
Backposts - At the back of an upright piano there should be three to six thick backposts. This gives the instrument extra strength. You need to check not only the number of the backposts, but also the width and depth of the wood. Solid spruce is one of the best types of wood for backposts because it has a high strength to weight ratio and resists splitting or cracking. But there are cheaper pianos that are made without backposts.
Soundboard - The soundboard is a thin piece of wood that reflects the sound made by the strings. The sound vibrations need to pass through the whole soundboard quickly without being inhibited, so only the highest grade wood with a straight, fine grain is used. Again spruce is the most common wood for piano soundboards but please be aware that solid spruce is susceptible to cracking and splitting in climates with extreme temperatures or humidity changes. There is also another type of soundboard that contains solid spruce and veneer. In this soundboard, the centre is made of solid spruce before a thin veneer of real spruce (generally 0.5mm) is added to each side providing strength, durability and retaining the sound projection qualities of the traditional soundboard. If you have any concerns about soundboards, the true test is to listen to the sound. Compare a few pianos next to each other with different types of soundboards and select one that sounds good to you. If you are happy with the sound that the piano makes, then you have no need to be concerned about the construction of the soundboard.
Ribs - The soundboard needs to support the pressure of the strings. It also needs to be free to vibrate so that sound waves travel through the wood and are amplified. Because of this, the soundboard is arched in the middle and is under tension with the help of ribs. You can see the ribs at the back of an upright piano, or underneath a grand piano. The ribs should be tapered at both edges to match the shape of the soundboard and thereby provide greater support in the centre (called the crown) where the soundboard is under greater curvature and pressure.
Bridge - Bridges are long pieces of wood that runs along the soundboard. When the strings vibrate, the sound waves travel through the bridge into the soundboard. This means that the bridge plays an very important part in sound amplification. The bridge should be made of rock maple and planed to conform to the shape of the soundboard. Bridges should be notched for each note, right along both sides so that the strings have an exact finishing point. Notching reduces the mass of the bridge and allows it to vibrate more freely. The bass bridge should be cantilevered, which means that the bass bridge uses longer strings and directs vibrations near the centre of the soundboard. This means that increased depth for the lower tones are produced.
Tuning Pins and Pinblock - The pinblock is designed to hold the tuning pins tightly enough so that the strings hold their tension and the piano stays in tune. The pinblock should be made of several plies of hard rock maple, quarter sawn for strength and placed cross-grain to each other. The number of highly compressed veneers or plies ensures that the pinblock is dense and less likely to be affected by moisture in any climate. This is very important to consider because if the pinblock expands, contracts and cracks then it is very expensive and difficult to repair and/or replace. To prevent rusting, the tuning pins should be nickel plated and treated with ‘blued steel’ which is an electronic method. This method helps prevent moisture problems and means they hold better in the wood.
Actions - The action is a group of parts that work together to hit the strings when a key is pressed. The action should be mainly made of wood. But in some cheaper pianos, the action may be made of synthetic parts, so it is important to check the durability of the parts.
Hammers - The hammer is part of the action. The hammer hits the strings and starts the sound ringing. The hammers should be evenly spaced and in line. The felt quality that is used in the hammers is very important. It has to be dense enough to prevent the strings from cutting into it but not too hard so that the tone is compromised. The best hammers should have two layers of wool felt; the outer layer, which is called the ‘hammer felt’ and is usually white in colour, and the inside layer called the ‘underfelt’ and is either red, green or purple in colour. The underfelt provides an amount of compression outwards to keep the hammer in shape as well as to ensure it rebounds when it hits the strings. The outer layers are applied with higher tension to give the hammer a balanced hardness and also ensure durability through repeated use.
Strings - The bass strings should have pure copper wound around the strings to produce the best tone. The strings should be spaced evenly but not be touching other strings. When you press a key, check the damper alignment and whether or not the hammers hit all the strings of all notes.
Agraffe - Almost all grand pianos and some top level upright pianos have agraffes. The agraffe is a guide at the tuning-pin end of the string that is screwed into the plate with holes through which the bass strings and low treble strings pass. They are designed to keep the strings perfectly spaced and assist in providing a good vibrating part of the string. Good quality agraffes are usually made of solid brass.
Pedals and Trapwork - Both the grand and upright piano has pedals at the feet of the piano located in the center of the piano. Some grand pianos have 3 pedals: the soft pedal (also called una corda), the sostenuto pedal, and the sustain pedal (pictured below from left to right) while others have 2 pedals: the soft pedal and the sustain pedal. Some upright pianos have only 2 pedals.
These pedals have various uses in playing the piano. They are listed below:
- The sustain pedal (right pedal on picture above) lifts the dampers from all keys, sustaining all played notes, and alters the overall tone by allowing all strings, even the ones not directly played, to reverberate.
- The soft tone (left pedal on picture above) shifts the entire action/keyboard assembly to the right so that the hammers hit two of the three strings for each note. This is to soften the note as well as change the tone.
- The sostenuto pedal (middle pedal on picture above) is only found in the grand piano. This pedal makes it possible to sustain selected notes so the pianist are able to play additional notes that are not sustained.
- Also in many upright pianos there is a middle pedal called the "practice" or celeste pedal. This pedal drops a piece of felt between the hammers and strings, greatly muting the sounds. It can be shifted into a locked position.
Before purchasing a piano, it is important to check that all the pedal functions work correctly and there are no squeaking or buzzing sounds after the pedals and keys are pressed together.
Transition Points - Transition points are two points on a piano where there is distinct change between the lower and upper strings. When you move from the bass strings to the low treble section, the structure of the piano changes. The lower treble strings are stretched across a separate piece of wood called the bridge. They should not be wound on like the bass strings and there should be three strings for each note instead of two. If you can hear the sound quality change at a transition point on the scale when playing each white note, then it is not a well constructed piano.
My next post will be about maintaining your newly bought piano and the best location to place it.