For something fast, that almost is better for Viennese, a great song is "Iris" by the Goo Goo Dolls. Julianne Hough and Helio Castroneves chose that song for their wonderful V Waltz on Dancing with the Stars. So it is a tad faster than a traditional waltz. Another one by Billy Preston and Syretta would be "With You I'm Born Again." This is a great one for a slow waltz, one I have used when teaching newlyweds for their first dance.