Maybe you could do something like asking for everything that's recorded after 1960 but before 1973. That's better, but it's still not really what you mean when you say around 1967. You would prefer tracks closer to 1967 than farther away.

This is where "fuzzy biases" come in. The goal with fuzzy biases, is create a playlists that approximately match a value. Generating biased playlists, is always a question of probability distributions. What we are really trying to do here is generate a playlist that fits normal distribution bell-curve.

Like this:

The horizontal axis is the year, the vertical axis is the probability of getting track of that particular. So the nearer to 1967 the track is, the better chance of it ending up in our playlist it has.Ok, another example.

I really just want to listen to some good straight up pop right now. No eleven minute epic folk ballads, no classical, no post-rock, just tight catchy songs. So I make a fuzzy bias to find songs that are about three minutes long.

Great. That's a pretty good mix, and I can refine it later with other biases.

The fairly vague "Strictness" slider indirectly controls the standard deviation of of the distribution.

How is this different than the old fashion method, just specifying a pair of strict biases?

To get all mathematical on you, that creates a playlist that matches a uniform distribution.

If you've never taken a statistics class and didn't follow any of this, let me summarize:

- pretty curves > boring rectangles.
- Apparently a math degree is actually good for something.
- Mom, you owe me an apology.