Nowadays most of the manufacturers put their custom UI on top of Android flavor which they include in phone like HTC has Sense UI, Samsung has TouchWiz and many more. In these UI you will find some custom made software which you might to get on other phones.
If you are bored by your HTC or Samsung’s apps and wants to try something more than you can download and install Sony Xperia Z1 custom Album and Walkman apps on your Android phone and best part of these apps is that you dont need to root or install custom ROM on your Android phone.
Android Jelly Bean OS
Procedure is very simple to install these apps, all you need to do is download and then connect your phone using USB cable and place these apps on your phone.
Now disconnect phone and with the help of file manager navigate to the apps and install them by following onscreen instructions. These apps are much smoother and easy to use, it wont replace your stock app.