     Running Instructions for the Call changes program.

This Desktop program shows an animated set of Church bells with their
ringers and allows users to practise Call changes to improve their listening
skills and change the order of ringing of the bells. It is intended for
those who are learning to ring or devise new calling sequences; it follows
the usual conventions and phrases used in the tower. A simple explanation of
the technique of bell ringing including many of the terms used are stored in
file Docs.Intro (in the application) for those who are not familiar with
the phrases.

Start the program by double-clicking on the !CallChnge icon to load an icon
on to the icon bar. The program detects the screen mode of your desktop
because it only runs in a 16 or 256 colour mode. If your desktop is in some
other mode you will see an error window saying  Please use a 16 or 256
colour mode. Click on OK to remove that window and then change the screen
mode before trying again.  The program works better in multi-sync modes.
Although it may run in other modes you could see bell wheels which are not
circular.

When the icon is loaded on to the icon bar, click <Menu> over it to see 
3 options, 

Info  - displays a small window with program details

Help  - displays this window with these running instructions

Quit  - stops the program

To Start:
click the <Select> mouse button over the icon on the icon bar to see a
window with title Call Changes where you set up the running parameters
before starting; these are: 
 - the number of bells to use, 
 - the key of the tenor, 
 - the volume of the sound, 
 - the length of the open lead gap, 
 - the strike rate.  
They are saved in a file from one run to the next.

#bells allows you to change the number of bells by clicking <Select> 
       on the up or down arrows, or <Adjust> will change it the other way.

The minimum number of bells is 5 because the program  performs changes by
waiting until the two bells to be swapped are both vertical between back-
and handstrokes and then interchanges them. This only happens for 5 or more
bells; with fewer bells two adjacent bells are never vertical at the same
time. (We may be able to use fewer bells if enough people ask for it, but we
started with 5 because you cannot make as many different changes on
4 bells.)

The maximum number of bells depends on the number of pixels across the
screen since the images are set 64 pixels apart, to use 16 bells you need
a screen width of 1024 pixels.

  mode   screen width  max number of bells

   27      640          10
   31      800          12
          1024          16 (absolute maximum).

Changing the key
Click on the icon next to the comment Tenor Key to see the range of
possible keys expressed in musical notation. Select the one you want which
should then appear in the small icon to the left. (See file Docs.Pitch
for how to make minor adjustments to the pitch.) 

Click on the arrow icons next to the Volume icon to change the volume
of the sound (Maximum 15, Minimum 0 ) Asking for zero volume will cause
a warning message The bells are silent with volume=0; this can be
useful if you are checking your calling sequence and do not want to annoy
others around you.

Click on the Try Tenor button towards the bottom of the window to hear the
sound.

Click on the arrow icons next to the Open lead icon to change the pause
before each hand stroke. Values from 0 to 2 in steps of 0.2 are allowed.
The standard open lead has a value of 1 meaning there will be pause of
one blow before the handstroke. Closed leads have a value of 0.

Click on the arrow icons next to the Strike rate icon to change the speed
of ringing. Values of 20 to 35 are allowed. A strike rate of 30 means that
30 rounds are rung in a minute and is about normal for six bells. For 12
bells the normal rate would be about 25 per minute.

Save changes and Replay are described later.

Click on the Look To icon to start the animation which takes place in a
special ringing window which cannot be moved; it takes all the Wimp time so
that the ringing speed is not affected by other Wimp activities which might
have been taking place.  

In Call Changes the two bells which are going to swap their position in
the order do so when they are both about to ring at handstroke; hence a
sequence always sounds twice, the handstroke then the backstroke in the same
order and will continue with the same sequence in pairs until a new change
is called.

The ringing starts half a second after this ringing window is set up.

One whole pull (two strokes) is rung before you can make any changes. This
simulates the time needed in a tower for the ringers to settle down and
correct their striking. Watch the ringers hands perform a Mexican Wave as
they ring the hand and backstrokes. Ringing stops at the end of a backstroke
after you have clicked over the word Stand.

At the top of the window your ringers and their bells are ready to start
ringing rounds; in this simulation, for simplicity all the bells and their
wheels are the same size although they each have a different pitch; in a
real tower the higher pitched bells are smaller with correspondingly smaller
wheels.

Instructions telling you how to change the order of ringing are at the
bottom of the green ringing window.

A line of bell numbers is shown just below the ringers. Click with the
<Select> mouse button near the dot between the bells which you want to swap
at the start of the next handstroke. Only one click can be made at a time in
accordance with normal Call Change practice.

After making your changes, click over the word stand to stop the ringing.
When all the graphics and sound have stopped you can click on the Close
icon of this ringing window.

Press <Escape> in an emergency and the ringing window will immediately
disappear.

The grey button at the bottom left in the main window, Replay, is used
to play back a composition after has been made: <Select> Replay to
put a tick mark in the box, then click over Look To.

With Replay selected the stored sequence will be followed; otherwise you are
expected to call your own sequence as you go along.

When replaying a composition, the bottom of the ringing window has
a white background, the first line has the number of stored changes and the
second simulates the calls made in the tower.

The button Save Changes is initially greyed out, it can only be used
after you have made a composition with some changes; it will not save just
rounds. After ringing some changes, save your composition to a file by
clicking over Save Changes to bring up a Save window with a file icon
which can be dragged to a filer window in the usual way.

To replay a previously saved composition, drag its filer icon to the main
window (or to the icon-bar icon). This overwrites any stored changes you may
have just made. The number of bells parameter will be changed to those used
when you saved the composition.

The format of the saved file is described with an example in
Docs.DataFormat; it is a text file which can be edited to make new
compositions or taken to the tower to remind you what to call.