Hi Anita,
Well, when you come to think of it, together with music there are three tempos going on, each changing at a different pace and interval.
The most dominant is the running tempo, the second in dominance is the music one, and the third is the heart rate. While the connection between the first and the second is very notable, not sure I noticed yet the connection between the second and the third. Analyzing charts of my running heart rate, it doesn’t seem to be affected much by the different music’s I played along the run. Seems that while I’m running, my heart is focused on steady pumping of blood to supply oxygen, proving it is mostly a pump. But then, I haven't tried it with Mahler’s 6th first movement yet!
On a different note, it reminded me of a music theory that shows that over the years there is a consistent increase in the tempo in which music pieces are performed. The tempo is highly correlated to the ever increasing pace of life and to inventions that made our life pace faster: train, car, plane, etc. So a Mozart Andante played in the time of Mozart is played today in a much faster tempo, demonstrating that we probably even walk today much faster than people used to in the past. Following the same logic, I wonder if runners prefer faster tempos.
Thanks for the suggestion, I will certainly try running with Mahler's 6th symphony and an opera or two and let you know of the results.