The organ at St James's Church is a three manual and pedal organ. It is situated in the chancel and contains hundreds of pipes of different sizes. When the organist plays a note on the keyboard, pressurised air travels by means of bellows to at least one pipe. The air vibrates in the pipe, making a sound that may be anything from a high-pitched whistle to a deep, low-pitched note, depending on the size of the pipe - the largest pipe producing the lowest note, and so on.
Each organ pipe produces a single pitch so the pipes are arranged in sets called ranks, each of which has a common timbre and volume throughout the keyboard range. Most organs, including our own, have multiple ranks of pipes of differing timbre, pitch and loudness that the player can employ singly or in combination through the use of controls called 'stops' (shown above).
The 'stops' beside the keyboards control the varieties of tone so that the organ may imitate various musical instruments, both wind and string. The stops have names, like 'diapason', 'vox humana', 'flute', 'celeste'.
The organist uses his hands on the three keyboards, called manuals (shown above), and his feet on the pedalboard beneath the keyboard, each of which has its own group of 'stops'. The organ's continuous supply of pressurised air allows it to sustain notes for as long as the corresponding keys are depressed, unlike the piano and harpsichord, the sounds of which begin to decay the longer the keys are held. The smallest portable pipe organs may have only one or two dozen pipes and one manual; the largest may have over 20,000 pipes and seven manuals.
Bernard Whitmill, who has a long association with the organ at St James’s, will spend much of 2017 deep in the organ chamber, meticulously repairing or replacing the parts of the instrument that are showing their age. The work can be split into two parts: the first is to repair the concussion bellows (these ensure the airflow is kept constant to the organ pipes at all times) and to move some of the pipes around so that the organ can sound even better than it did. This should be good news for members of the congregation who sit in the north transept as they will no longer be deafened when the trumpet pipes are used, (they were previously near the front of the organ). These have been moved towards the back of the organ and also higher up in the organ chamber, which is where they would normally be placed in a good organ layout. Have a look at the photo album.
Inside the organ chamber