Clockwheels: how radio hours are actually built

A clockwheel is a diagram of one hour. Not a specific hour — any hour of that type. It says: music, sweeper, two more songs, talk break, news at the top, jingle, and so on round the circle.

It is the single most important idea in radio programming, and it is why professional stations sound consistent and amateur ones do not. A station built from playlists sounds like a playlist. A station built from clocks sounds like a station, because a listener who tunes in at 14:20 on Tuesday and 15:20 on Friday hears the same *shape* both times even though every element is different.

Why not just a long playlist

A playlist is a list of items in an order. That works for an hour, and then you need another one, and by the third week you are maintaining hundreds of them, all slightly different, none of them expressing what you actually meant.

What you actually meant was a rule. *Two songs, then a jingle. News on the hour. A sweeper out of every break. Nothing older than 1995 before 6pm.* Those are structural facts about the station that should not have to be restated 8,760 times a year.

The clock holds the structure; the library fills it. Change the clock once and every hour that uses it changes.

What goes in a slot

A slot points at a source rather than at a specific piece of audio:

A playlist — pull the next item from this rotation. Not "play this playlist"; pull one item from it. That distinction is the thing people take longest to internalise, and it is what lets a clock interleave three different rotations.

A folder — pull from a filed part of the library directly, so a genre folder does not need a playlist built to mirror it.

A jingle, sweeper or ident — the station's own furniture.

A specific item — a fixed piece of audio, for when the answer really is "this file".

A talk break — the next voice link queued for this show. If nothing is queued, the clock moves on rather than leaving a hole.

An external stream — audio you do not host, fetched at the moment it airs. A weather bulletin or a news feed published at somebody else's URL. Pin it to :00 and that is your news on the hour.

Rotation and separation

The reason a clock does not simply pick at random is that random sounds broken. Genuine randomness plays the same artist twice in ten minutes surprisingly often, and listeners notice every time.

So pulls are governed by two kinds of rule:

Rotation decides which item is next — least recently played first, so the library is worked evenly rather than favouring whatever sorts to the top.

Separation decides what is not allowed yet: not the same track within some window, not the same artist within a shorter one. RadioHost Studio's folder pulls use two hours for the track and forty-five minutes for the artist, and play least-recently-played first. Those figures are fixed because a folder pull is meant to be the simple option; when you need to tune the numbers or combine several sources, that is what a playlist is for.

Separation is the invisible work. Nobody has ever praised a station for not repeating an artist. Every listener has noticed one that did.

Pinned minutes

Some things happen at a time, not in a sequence. News at :00. A traffic bulletin at :25. A network junction.

A pinned slot airs at its minute instead of taking its turn in the rotation. In a well-behaved system this does not mean cutting anything off — the clock reaches the pinned slot at the first track boundary after the minute, so a song still playing at :00 finishes first.

Which creates a small, real problem: news pinned to :00 actually starts at :02 or :03, at a different minute every hour, depending on where the music happened to land.

Back-timing

Back-timing is the fix, and it is quietly clever.

As a pinned minute approaches, the clock stops picking freely and starts picking songs *short enough to end before it*. The last one finishes by itself, right on the minute, and the pinned slot opens on time with nothing faded and nothing cut.

The setting is how many minutes ahead it starts doing this. Zero turns it off; five is the usual value. Earlier and your short songs get overplayed for no benefit. Later and there is not enough runway to land cleanly.

Occasionally there is a forty-second hole and every song in the library is three minutes. For that, a filler folder — jingles, sweepers, station idents — closes the gap. Without one, the pinned slot simply starts late. It never goes silent either way.

Back-timing needs something to aim at: with no pinned slot in the clock, it has nothing to do.

Designing a clock that works

Leave at least one slot unpinned. A clock where everything is pinned has no rotation to fill the time between the pins, and the station falls through to its fallback.

Build a small number of clocks, not one per hour. Most stations need four or five: breakfast, daytime, drive, evening, overnight. Assign them across the week from the schedule.

Check the lap. The slots should add up to roughly an hour. A clock that laps in fifty minutes plays its first slot twice; one that laps in seventy never reaches its last.

Make overnight a different clock, not the same one with the talk removed. Overnight listening is longer-session and less attentive. Fewer interruptions, longer music sweeps, and no forward-references to a show that already happened.

Frequently asked questions

What is the difference between a clock and a playlist?

A playlist is a pool of items with rotation rules. A clock is the structure of an hour that pulls from those pools — one item at a time, in a fixed shape, with jingles and talk breaks in between.

How many clocks does a small station need?

Four or five is enough for most: breakfast, daytime, drive, evening and overnight. Add more only when a daypart genuinely sounds different, not because the schedule has more rows in it.

Why did my pinned news bulletin start two minutes late?

Because a song was still playing at the pinned minute and nothing is cut off mid-track. Turn on back-timing so the clock chooses short enough songs to land on the minute.

What happens if the external news feed is down when the slot comes round?

A well-built system steps over it and plays the next slot rather than waiting. Your station does not go quiet because somebody else's server did.

Can I use clocks and live shows on the same station?

Yes, and that is the normal arrangement. Clocks cover the unattended hours; a live presenter takes over when they connect, and automation resumes from wherever the schedule says it should be when they disconnect.