Well, I guess the posts above yours answered my question, but you raise an entirely different one, do not all systems work the way the two I have worked with handle things? I've worked with Zara and Station Playlist.
With Zara, all you have is a playlist that contains various file types, which the system knows what to do with. I've heard of it done where you can use timed events to create some form of a schedule, but I'm not sure events were intended to be used this way. Unless you manually schedule your playlists by hand though, there's really no schedule, just a bunch of files that you can somewhat control the order of.
Both Selector and MusicMaster have the ability to set a highly complex set of clocks and rules.
Songs are coded on artist keyword, station category, day-parting rules (such as "nights only" or "not in AM Drive), year of release, tempo, type, style and other definable qualities a programmer wants. Many categories are definable with each one having specific rules on things like rest.
Rules can specify how many songs of each tempo or style or era or category or other quality go in each hour and where in the hour and next to what other qualities. Example: no B Current next to a new release. No slowest tempo within 4 plays of another. And so on.
Then you have clocks, as many as one for every hour of the week but usually less, such as one or two per daypart and special ones for holidays and weekends. The clocks have rules as to which category of songs go where in the hour (Example of categories: Powers, B Currents, A recurrents, B recurrents, power gold, regular gold, secondary gold, Fill, new releases).
Some songs that the PD wants to play less can be rotated automatically in and out of rotation on a calendar-based schedule. Or songs that are borderline between being an A Recurrent or B Recurrent can spend a period in each category and rotate back and forth.
In Station Playlist, Creator handles the scheduling and Studio plays the tracks at the appropriately scheduled time. To schedule a playlist, all you have to do is set up your rules then hit schedule, and by default it will schedule for two days. I've never worked with it using traffic software, but I would imagine that the data from the traffic software is also integrated into the playlists when they are scheduled, as they are simply M3U8 lists underneath. Do some of the bigger scheduling programs still work this way, or are they completely different from the way Station Playlist operates? I do know that Creator has some limitations that the bigger systems do not, but again, is the principal the same or completely different?
What you get for little or no money is little or no control over the playlists. What you get with Selector or MusicMaster is almost infinite control over.
Traffic is even more complex, as it controls how billing will be done as well as spot scheduling. Good traffic packages are very expensive. But they have some similarities, such as running spots in specific dayparts, hours or even times and protecting against coded competitive accounts. Traffic systems take the client contract and then perform scheduling based on the dates, times, specific pieces of copy and the like.
In both traffic and music, there is plenty of need for the editing of each day's log. With music, there may be unscheduled positions that could not be done automatically and that require manual editing. With traffic, there may be the need to do make goods for missed spots, or to figure out how to handle an oversold hour.