Cognitive Daily has an interesting series of posts on tempo and how it is detected. Since tempo is a relevant topic here, I thought I would pass it along.
Here are some excerpts:
They took 23 Scottish fiddle songs and played them on a synthesizer as marked in their musical scores. They then artificially slowed and speeded each tune’s tempo by 10, 20, and 30 beats per minute. Student volunteers listened to each song, as well as the original version, in random order (so they weren’t listening to the same song over and over again). They were simply asked if the song sounded too slow or too fast.
An analysis of the measurable musical features of the songs found that most features (for example, whether the music was in a major or minor key) bore no significant relationship to the ideal tempo of the song. The only feature that did correlate significantly was the number of descending intervals, which correlated with tempo at r = 0.49.
So how is the optimal tempo picked?
Do we have an internal clock that runs at 100 beats per minute? Quinn and Watt’s results suggest that if we do, we don’t apply it willy-nilly to every song we hear. Instead, something about content of the songs suggests an appropriate tempo. While their research doesn’t give us a definitive answer as to what that tempo might be, they do have some hunches. If a song has many “strong” events — events that vary simultaneously across several musical dimensions — then the authors suggest that these sorts of songs might be preferred at a slow tempo, compared to songs filled with weak events. Listeners want to savor those nuances, and can only do so when the song is played slowly enough.
While the makeup of an ideal tempo is still being investigated, it is clear that people are extremely accurate at remembering tempo and detecting tempo changes, but only within certain parameters. From personal experience, I know that extending a tempo change over 5 or 6 minutes can make it barely noticeable. This is one feature of an effective relaxation session, where easily detectable changes in tempo can act to keep the listener too engaged to relax or sleep.
However, in some cases tempo changes are used in the middle of a session to keep the user awake. This is a common practice for the middle of theta sessions, where many people find themselves dozing off. Modulating the tempo up and down within the theta range is a good way to keep the listener conscious, but still relaxed.
Here are the links to the Cognitive Daily posts. As usual, they have uploaded some online tests to replicate the results of the studies. Try them out for yourself: