How do I override the default number of items to be listed on an archive.php page? [duplicate]

You can hook into pre_get_posts and modify the query. Your hooked function will receive a WP_Query object as it’s only argument. You can check to see if you’re on a the correct post type archive and modify away.

Something like this:

<?php
add_action('pre_get_posts', 'wpse63675_pre_posts');
function wpse63675_pre_posts($q)
{
    if(!is_post_type_archive('your_album_type'))
        return;

    $q->set('posts_per_page', 20); // or however many you want
}

You can drop the above in your functions.php file or a plugin. Use with caution.

I wrote a plugin that takes care of this for you. It does the above, but with a set of fields in the admin area.