To recognize a favorite contact just by listening the specific ringtone, allocated to that contact, is a good idea. In Android devices, you may set different ringtones for difference contacts so that you may recognize the specific caller by just listening the ringtone, allocated to that contact.
Now, you may do so, easily, but if you need some help, just see the instructions.
1: Tap the icon of ‘Phone Dialer’ on the Home screen of your Android 5.1 Lollipop device to open up the ‘Phone Dialer’ app screen.2: At the ‘Phone Dialer’ app screen, tap the interface settings button, placed on the top right corner of the image of the contact with which you want to add a specific ringtone. It will open up the interface screen of the contact.3: On the interface screen of the said contact, tap the ‘Edit’ button, placed near the top right corner of the contact interface screen. It will open up the ‘Edit contact’ screen. 4: At the ‘Edit contact’ screen, again tap the settings button. It will open up a popup menu.5: Tap the ‘Set ringtone’ in the popup menu. It will open up a ringtone list screen.6: See the ‘Default ringtone’ is already selected. This is the ringtone which is being applied to all the contacts.7: If you want to set a specific ringtone for the said contact, just scroll up or down and select a ringtone. To listen the ringtone before final selection, tap the name of the ringtone.Now, upon listening this ringtone, you may recognize the caller even before seeing the Android device screen.