Ringdroid for PC is a great way to come up with new ringtones. This is an open-source app, which helps users to compose their own ringtones. And not just this, you can even use the app to compose personalised alarm tones, various sounds for notification tones, and you can do all of this with the help of the already existing audio and music files on your device.
The app even allows users to record stuff, and then use it to compose custom ringtones and notification alert tones. The app accesses the contacts on your list, so that you can automatically assign particular ringtones to all your individual contacts. The app also uses your network communication to send some usage statistics anonymously, which can be changed in the settings at the Privacy menu.