OS X Yosemite brings a refresh look with a flatter and more translucent design. Bundled Apple OS X apps are updated to keep up with the new look. iTunes is no exception, with changes that might take some adjustment to get used to.
The mini player icon is gone from the top left corner of iTunes window. To switch iTunes to mini player mode in OS X Yosemite, you click on the album artwork.
By default, the mini player displays a not-so-mini album artwork. The size is acceptable if you have a 27 inch screen. To make iTunes player truly small, click on the double-arrow icon.
iTunes mini player will now shrink to the size and look that we’re familiar with.
Click on the same double-arrow icon to toggle back to the album artwork look.
To switch off mini player mode and return to full window, click on the x button.