With the advent of cell phones in the late 1920's, the landscape of phone ringtones changed again. The first mobile phones used monophonic ringtones that could only play a note or a single tone. These monophonic ringtones were limited due to the limited technological capabilities of the time, but they nevertheless created a new era of customization as users could choose from a limited selection of preloaded ringtones.
With the continuous development of mobile phone technology, the possibilities for telephone ringtones have become more and more diverse. Polyphonic ringtones were introduced, which could play multiple tones at once, allowing for more complex melodies. This gave rise to a veritable ringtone industry, with both preloaded and downloadable ringtones available in a wide range of genres and styles. Pieces of music, sound effects, voice snippets and even humorous sounds have become popular choices for custom ringtones.