Numeric Field Operators in D6 Views 6.x-2.12

Hi. I need to filter a field that has been stored as varchar using Views numeric operators (ideally the "Is Between" operator). I have run across several posts re: related situations but can't seem to figure out how to apply these ideas to my situation, which seems to have been complicated by the way the content type (Audio - the last, incomplete version) was designed (the Audio and ID3 modules work in concert to extract and store MP3 file metadata; the Audio module stores all metadata in a varchar column in a table "metadata"):

mysql> describe audio_metadata;
+-------+------------------+------+-----+---------+-------+
| Field | Type             | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+-------+
| vid   | int(10) unsigned | NO   | PRI | 0       |       | 
| tag   | varchar(45)      | NO   | PRI |         |       | 
| value | varchar(255)     | NO   | PRI |         |       | 
| clean | varchar(255)     | NO   | MUL |         |       | 
+-------+------------------+------+-----+---------+-------+

One thing I would really like to know: how/where/when does Views assign an operator type to a field?

The developer of the Audio module has completely stopped answering support requests, and for D7 the module is deprecated. However aside from this seemingly trifling issue, this module is perfect/working very well for the needs of this site which for various reasons pretty much needs to be in D6.

It seems that the prescribed D6 way of doing this sort of thing involves writing a custom module using hook_views_data_alter(). I could really use some help understanding how to apply this method to my use case - for one thing I don't really get how Views is able to see these metadata fields (but it can) as they are being stored separately from the available fields one can see when managing fields for the Audio content type - I really need to figure out how hook_views_data_alter() can get at these fields.

Or, there does seem to be a half implemented solution within the module itself... given the addition of a metadata tag to an array like so (code from audio.views.inc):

$numeric_tags = array('track', 'year');

... the author of the Audio module seems to have intended to provide a way of replacing other metadata filter handlers with numeric handlers for a given metadata "tag" type:

    // Use different handlers for numeric tags.
    if (in_array($tag, $numeric_tags)) {
      $tables["audio_metadata_$tag"]['sorts']['value']['handler'] = 'audio_views_sort_handler_numeric_tag';
      // Set notafield to TRUE so that our handler can add the field.
      $tables["audio_metadata_$tag"]['fields']['value']['notafield'] = TRUE;
      $tables["audio_metadata_$tag"]['fields']['value']['query_handler'] = 'audio_views_field_query_handler_numeric';
    }

... however this doesn't seem to work as is even for the 2 tag types the author left in the array. Any help understanding why not or troubleshooting that would be greatly appreciated.

Anyone? Thanks much for any help.