The Even/Odd Rule

(update: This article was written BEFORE music scheduling software took over playlist control. Today, most schedulers will show us a Category Rotation chart, as MusicOne does. On it, you can see what the repeat-pattern is for each group. Pay attention to it for that grid is the most important screen in music radio formatting.)

I want to tell you about a mistake I've watched programmers make over and over, usually without knowing they're making it. They set up a Power Current rotation with, say, ten songs. They format four of them per hour. It feels right. The math seems fine. And then, three weeks later, they have a vague sense that something is off. Their heaviest songs keep showing up at the same time of day.

They're not wrong. The problem has a name. It's the Even/Odd Rule, and once you understand it, you'll never forget it.

Here's how it works. When you have an even number of songs in a tight rotation and you format an even number of slots per hour, the songs start to lock into fixed positions across the clock. Song #5 plays at :10 and :40 this hour, and it tends to play at :10 and :40 tomorrow, and the day after. Listeners who tune in at the same time each day start hearing the same songs in the same order. Not because you programmed it that way intentionally. Because the numbers happened to line up.

The fix is simple. Use an odd number of songs when you're formatting an even number of slots per hour. Use an even number when you're formatting an odd number. The mismatched pairing keeps the math from settling into a groove.

A concrete example

Say you're running four Heavy Currents per hour. That's an even number of slots. You want 13 songs in the category, not 12 or 14. Thirteen is odd. Playing those 13 titles at four per hour gives you a 3:15 turnover, and more importantly, each song drifts forward through the clock over the course of the week. Monday morning drive is not the same as Monday midday. Tuesday's lineup isn't a copy of Monday's. The rotation breathes.

If instead you put 12 songs in Heavy and formatted four per hour, song #1 would complete a full cycle in exactly three hours. Three goes into 24 exactly eight times. So song #1 plays at the same minutes past the hour, eight times a day, every day. Your morning drive listener hears it. Your afternoon drive listener hears it. Every regular listener hears it at roughly the same clock position. That's the definition of listener burnout without the listening time to justify it.

The rule applies to any tight rotation. Gold categories, Power Recurrents, anything where the songs turn over frequently and the repetition factor matters. Tight rotations are where this bites you hardest, because those are the songs with the most exposure. Getting those wrong is the most expensive mistake in your format.

What to do with this today

Pull up your Heavy Current category. Count the titles. Count how many slots per hour you're formatting. If both numbers are even, or both are odd, you have a problem worth fixing.

Adding or removing a single song from the category is usually all it takes. You don't need to rebuild your clocks or restructure your format. One song in, or one song out. That's the whole correction.

Some programmers resist making the change because the rotation feels balanced on paper and they don't want to tamper with it. I understand that. But a rotation that looks balanced on paper and sounds predictable on air isn't balanced. It's stuck. The Even/Odd Rule is what gets it moving again.