Differing behaviours of the previous song button

Question

I remembering discovering this functionality as a child when I operated a DVD player and I've never fully understood it. Recently I've been tasked with writing a short tutorial on the basic operations of an iPod and the question has come up again.

The button in question is |◀◀ or on iOS, ◀◀. The behaviour of the button seems to vary with the current time of the media being played. For instance, the logic of the button in SoundCloud on Android seems to be:

if (nowPlaying.currentTime < 2 && positionInQueue > 0) {
    nowPlaying = queue[positionInQueue--]; // play previous media in queue
} else {
    nowPlaying.currentTime = 0; // restart the media
}

It's similar for iOS except that the condition appears to be nowPlaying.currentTime < 3.

On Windows Media Player, the button always tries to play the previous item and if the first item was playing, it stops playback.

Here is a screenshot of SoundCloud on Android and the default iOS 7 music application:

And here are the controls for Windows Media Player:

Questions

1. What is the significance of the vertical bar (or lack of) that the arrows point towards? I remember back when VHS was in use, the two triangles meant "Rewind", however we aren't dealing with physical videocassettes here so the only thing that would make sense with that is "play backwards", which isn't a feature.

2. The main question: Why does the behaviour of the button differ with the current time of the media?

Answer 1

What is the significance of the vertical bar (or lack of) that the arrows point towards?

Usually, the vertical bar's significance is that it jumps back/forth to a defined point. E.g. to the beginning of a song. Without the bar, the point to jump to isn't defined and it just keeps rewinding/fast forwarding until another user action takes place.

This being said, I observed that this is the fact whenever both types of buttons (with and without the bar) are present. Whenever only one type is present the buttons seem to be used interchangeably.

Why does the behaviour of the button differ with the current time of the media?

I could imagine that most users pressing the ◀◀ button want to restart the song that is currently being played. Otherwise they would have to press back and then forward to achieve this. If you're on position 0, restarting the song wouldn't make sense so the previous song gets started. Personally I have never liked this behaviour, but it seems to be have become to some sort of standard now.

Answer 2

Traditionally:

|◀◀ means: Skip to the start or previous file/track. Press it once to go to the beginning of the current item, press it twice to go go the previous item.

◀◀ means: Rewind.

So why the vertical bar? Back in the days on tape, both Skip and Rewind would activate the same physical mechanism (moving the tape backwards). ◀◀ would continue indefinitely, and |◀◀ would continue until the next "marker", which would either be the beginning, a part of (relative) silence, or some user-defined marker.

On Itunes both of these actions are done with ◀◀. Click it for skipping, hold it for rewinding. And skip to the previous item instead of to the beginning of the current item if we are in the beginning of the song.

The logic here is:

• Most people who are using |◀◀ very early in, don't want to play that song again but rather want to go to the previous song.*

• Most people who are using |◀◀ in a later part of the song want to play that song again (or here the intro, play if from the beginning, etc.)

  • This was always a big annoyance on cd players, where you had to press |◀◀ twice to hear the previous song.

Answer 3

You want someone who designed and implemented it or just a guess?

Ad. 1 - Either and intention to explain that you're going through the list, not rewinding like on tape recorders (Windows are oldtimers.) See some old player UI, with both sets of arrow buttons.

Ad. 2 - Apple took users and did research (which might ended 70:30, you can never know) and iterations and fights around a table to get there the "err, not this one" correction functionality, because they do business with these small things.

Do we have similar thoughts or you found other potential reasons?