Mark and Marko, Hi:
Thanks for the solutions. They both worked. I didn't understand that the enclosing brackets were necessary. I knew something was wrong each time I entered a CUSTOM expression in the IMPORT/EXPORT area, it was dismantled and assembled across multiple CUSTOM expressions. Thanks for pointing me in the right direction and for the insight into the expression language. As others have discovered, it a painful process. Thankfully, there are mates like you that step up.
In addition, I came up with another alternative to solve my quest. Within the 'Search List' view, I established a column called 'Within Artist' based on an expression which highlights ARTIST groups, 1 or 2+, by LISTCOUNT within the ARTIST field. As a bonus, LISTCOUNT displays exists for all the types of 'Artist Delimiters' being tracked. The pictures below are window snaps of the navigation, expressions, and results. Note, the 2+ LISTCOUNT for ";" (the semicolon solution you provided) matches the the 2+ LISTCOUNT for 'All Artists Delimiters'. This is proof that your solutions are consistent with the LISTCOUNT results found in the 'Within Artist' column.
Thanks again for your replies and your help.
Cheers,
Lawrence