Traditionally, the name Viennese Waltz refers to a very specific musical genre: The relatively fast Waltzes of the the Romantic era in Vienna. The music is usually written in 6/8 time at a tempo of 29-30 measures per minute, although it is sometimes written as a fast 3/4 at 58-60 measures per minute. It is almost always instrumental, written for orchestras of varying sizes. The most well-known of all composers of Viennese Waltz music is Johann Strauss, responsible for such notorious works as the Blue Danube and Tales From the Vienna Woods.
But the music of Johann Strauss and similar composers of the 1800's only acounts for a fraction of the music which is popular these days for dancing the Viennese Waltz. Dancers are enjoying many different styles of fast 6/8 Waltz, much of which is not Viennese at all. The music can be instrumental or vocal, Classical, Celtic, Country or even a "Top 40" hit.