This would be a cleaner way to see what is going on and easy to extend

AND('1'=
     CASE(LeadSource,  /* set Case result to '1' if text field is required */
          'Wholesaler',CASE(Lead_Source_Details__c,
                                        'Other','1',
                                        '0'),
          'Personal Referrer','0',
          'Trade Show/Event','1',
          'TBP Event','1',
          'Website','0',
          'Other','0',
         '0') ,
     ISBLANK(TextField__c)
)


Three tier Validation Rule / Validation chain?
It may seem as a kinda dumb question, and I'm totally aware of this. But, what I'm going to ask may be specific enough to not get closed:

I've been playing guitar and also a few other instruments for quite a while now, but I just can't sing. I can hear a melody in my head, but even if I try to hit the first note, I will fail very often. Now what I want to ask is, can anyone learn to sing in a manner that "won't hurt the ear of a non-musician"? I'm not asking if anyone could be the next Freddie Mercury, but does anyone have the ability to sing some backing vocals if needed, without just sounding terrible?

I always find it hard to get question on music get to the point, so i'll try it with this: Can anyone achieve semi-professional level of singing, even if one doesn't have a "good" voice?
