Glossary view from field other than title Drupal 7

I was googling for a long time for this and I didn’t find an answer. Finally I got it.

I really don’t understand how it works but it works.

My problem was that the glossary mode in views seemed to only work with title field of node. I wanted to set glossary mode to look for text in field_apellidos (CCK field). What I did was:
I deleted contextual filters for both Page and Attachment display (content: title)
For both «Page display» and «Attachment display» I created a contextual filter for my custom field and set «glossary mode»
The contextual filter for Page display is where I set the default behavior. i.e. show all items.
The contextual filter tor Attachment is where I set «Display a summary». This is what makes the «A | B | C |… » block at top.

This is the export of my example

$view = new view;

$view->name = 'glosari_artistes_2012';

$view->description = 'A list of all content, by letter.';

$view->tag = 'default';

$view->base_table = 'node';

$view->human_name = 'Glosari artistes 2012';

$view->core = 0;

$view->api_version = '3.0-alpha1';

$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */



/* Display: Master */

$handler = $view->new_display('default', 'Master', 'default');

$handler->display->display_options = 'none';

$handler->display->display_options = 'none';

$handler->display->display_options = 'views_query';

$handler->display->display_options = FALSE;

$handler->display->display_options = 'basic';

$handler->display->display_options = 'Reinicialitza';

$handler->display->display_options = 'full';

$handler->display->display_options = 36;

$handler->display->display_options = 'list';

$handler->display->display_options = 'artista';

$handler->display->display_options = 'artistas';

$handler->display->display_options = 'artistas-wrapper';

$handler->display->display_options = 'node';

$handler->display->display_options = 1;

$handler->display->display_options = 0;

/* Relationship: Contingut: Autor */

$handler->display->display_options = 'uid';

$handler->display->display_options = 'node';

$handler->display->display_options = 'uid';

/* Camp: Contingut: Títol */

$handler->display->display_options = 'title';

$handler->display->display_options = 'node';

$handler->display->display_options = 'title';

$handler->display->display_options = 1;

/* Camp: Usuari: Nom */

$handler->display->display_options = 'name';

$handler->display->display_options = 'users';

$handler->display->display_options = 'name';

$handler->display->display_options = 'uid';

$handler->display->display_options = 'Author';

$handler->display->display_options = 1;

/* Camp: Contingut: Updated date */

$handler->display->display_options = 'changed';

$handler->display->display_options = 'node';

$handler->display->display_options = 'changed';

$handler->display->display_options = 'Last update';

$handler->display->display_options = 'large';

/* Sort criterion: Contingut: Cognoms (field_apellidos) */

$handler->display->display_options = 'field_apellidos_value';

$handler->display->display_options = 'field_data_field_apellidos';

$handler->display->display_options = 'field_apellidos_value';

/* Contextual filter: Contingut: Cognoms (field_apellidos) */

$handler->display->display_options = 'field_apellidos_value';

$handler->display->display_options = 'field_data_field_apellidos';

$handler->display->display_options = 'field_apellidos_value';

$handler->display->display_options = 'fixed';

$handler->display->display_options = 'A';

$handler->display->display_options = 0;

$handler->display->display_options = '0';

$handler->display->display_options = 'unformatted_summary';

$handler->display->display_options = FALSE;

$handler->display->display_options = '25';

$handler->display->display_options = '1';

$handler->display->display_options = 1;

$handler->display->display_options = '1';

$handler->display->display_options = 'ucfirst';

$handler->display->display_options = 'ucfirst';

$handler->display->display_options = 0;

$handler->display->display_options = 0;

/* Filter criterion: Contingut: Tipus */

$handler->display->display_options = 'type';

$handler->display->display_options = 'node';

$handler->display->display_options = 'type';

$handler->display->display_options = array(

'artistes' => 'artistes',

);

/* Filter criterion: Contingut: Pinotxo (field_pinotxo) */

$handler->display->display_options = 'field_pinotxo_value';

$handler->display->display_options = 'field_data_field_pinotxo';

$handler->display->display_options = 'field_pinotxo_value';

$handler->display->display_options = '2012';



/* Display: Page */

$handler = $view->new_display('page', 'Page', 'page');

$handler->display->display_options = FALSE;

/* Capçalera: Global: Text area */

$handler->display->display_options = 'area';

$handler->display->display_options = 'views';

$handler->display->display_options = 'area';

$handler->display->display_options = TRUE;

$handler->display->display_options = '2010 | 2011 | 2012';

$handler->display->display_options = 'full_html';

$handler->display->display_options = 0;

$handler->display->display_options = 'glosari-artistes-2012-Pinotxo';

$handler->display->display_options = 'normal';

$handler->display->display_options = 'Glossary';

$handler->display->display_options = '0';



/* Display: Attachment */

$handler = $view->new_display('attachment', 'Attachment', 'attachment');

$handler->display->display_options = 'some';

$handler->display->display_options = FALSE;

/* Contextual filter: Contingut: Cognoms (field_apellidos) */

$handler->display->display_options = 'field_apellidos_value';

$handler->display->display_options = 'field_data_field_apellidos';

$handler->display->display_options = 'field_apellidos_value';

$handler->display->display_options = 'summary';

$handler->display->display_options = 'fixed';

$handler->display->display_options = 'A';

$handler->display->display_options = 0;

$handler->display->display_options = '0';

$handler->display->display_options = 'unformatted_summary';

$handler->display->display_options = FALSE;

$handler->display->display_options = '25';

$handler->display->display_options = '1';

$handler->display->display_options = '|';

$handler->display->display_options = 1;

$handler->display->display_options = '1';

$handler->display->display_options = 'ucfirst';

$handler->display->display_options = 'ucfirst';

$handler->display->display_options = 0;

$handler->display->display_options = 0;

$handler->display->display_options = array(

'default' => 'default',

'page' => 'page',

);

$handler->display->display_options = 0;

$translatables = array(

t('Master'),

t('more'),

t('Apply'),

t('Reinicialitza'),

t('Sort by'),

t('Asc'),

t('Desc'),

t('Items per page'),

t('- All -'),

t('Offset'),

t('author'),

t('Títol'),

t('Author'),

t('Last update'),

t('Tot'),

t('Page'),

t('2010 | 2011 | 2012'),

t('Attachment'),

);