Topsy 3

Specification

Melody

The melody section supports 22 notes covering about two octaves.  Each note can be sounded on up to three pipes and a glockenspiel.

Bourdon

These are the main melody pipes and stand across the front of the organ.  They are stopped pipes in that they have a plug at the end.  Stopped pipes sound an octave lower that open pipes of the same length. So they take up less space.  Stopping a pipe also changes the tone, generally making it less strident.

These pipes are arranged in the traditional fan formation with the largest and deepest pipes in the centre tapering off to the smallest at each side.

Celeste

The celeste pipes are identical to the bourdons.  They sound the same notes but are tuned slightly off to produce a beating sound.  In this organ they can sound with the bourdons but can be turned off when not required.  They are mounted behind the bourdons.

Octave

The octave rank consists of 22 pipes.  They are tuned one octave higher than the bourdon and celeste and coupled with the equivalent notes in the bourdon section.

Glockenspiel

The glockenspiel is mounted across the front of the organ.  It covers the same range as the bourdons to which it can be coupled when required.

Accompaniment

The accompaniment section has twelve stopped pipes cover the octave below the melody section.  These are mounted at the back of the main pipe space in the organ.

Counter-Melody

The counter-melody section has fourteen open pipes, tuned around Middle C.  They can provide a contrast to the main melody section, having a stronger sound.  They are positioned in front of the accompaniment section and along the right hand side.  The longer pipes at the side are folded over below the top of the cabinet.

Bass

There are just eight bass pipes.  These are stopped pipes to reduce their length but are still the largest in the organ.  The four smaller pipes are mounted on the left of the cabinet, folded over to fit under the lid.  The other four are mounted horizontally underneath the main windchest.

Percussion

Wood Block

A small wood block is mounted in the top right hand corner at the back of the organ.  It has two beaters to allow rapid sequences to be played.

Triangle

A triangle is mounted on the right hand side, in front of the counter-melody pipes.

Snare Drum

A snare drum can be added externally.  It has one beater that strikes the centre of the drum, replacing the triangle, and two more, near the rim, that replace the wood block.

Effects

Vibrato

The vibrato acts on the melody section.  It consists of a small bellows connected to the windchest and operated by an electric motor.  It does not actually contribute any air to the system but just causes the pressure to fluctuate.

Tremulant

The tremulant feature chops continuous notes into a series of rapid pulses.  It operate electronically, interrupting the electrical signals to the pallet magnet that control the air to the individual pipes.

Control

The organ supports 64 MIDI notes.

Most of these are used to sound the expected musical notes but there are some exceptions.  The top octave is used to operate counter melody section which actually sounds three octave lower that the MIDI note so that it overlaps the accompaniment and melody ranges.

Four notes are reserved to operate the percussion instruments.

Four more  notes are used to turn the celeste, octave and glockenspiel on and off.

The vibrato and tremulant effects are each controlled by discordant pairs of normal musical notes.  If these notes are sounded individually then the appropriate pipes will play.  However, if the pair is sounded then the tremulant or vibrato will be activated instead.