What A-B repeat is

A-B repeat is an old feature of CD players and tape decks: press A where a passage starts, press B where it ends, and the player repeats the part in between until you cancel. It is a quick way to drill a phrase, and YouTube has no such button of its own. YouTube can repeat a whole video, but it cannot repeat a section of one.

Using it in Chrome

Add PitchShed, open a video and click its icon. In the Loop row, Set A takes the time the video is at right now, and Set B does the same once A is set. After both are set, the buttons show the times and the repeat is on. Click Loop OFF to play on, or clear to remove both points.

Getting the points exact

You will rarely hit the right spot with a click. Use the small arrows beside each point to move it by 0.1 seconds while the loop runs, until the repeat starts and ends where you want it. Two or three taps are often enough.

Works with the speed control

A loop becomes more useful when it is slower. The Speed row sits right above it, so you can slow the repeated passage to 70 % and keep the pitch where it was.

The same loop next time

The loop is saved with the song, so the points are back after one click on the icon when you return to that video.

A cleaner way to drill

Many players set the loop a beat wide on each side of a hard phrase, so that they hear how the music leads into it and out of it. If the phrase then feels easy, tighten the points. Moving a point by a tenth of a second is quicker than clicking on the video bar again.