The term polyphonic has several related, but different, meanings.

Merriam-Webster defines polyphony as "a style of musical composition employing two or more simultaneous but relatively independent melodic lines."

Wikipeda defines polyphony as "a musical texture consisting of two or more independent melodic voices, as opposed to music with just one voice (monophony) or music with one dominant melodic voice accompanied by chords (homophony)."

A second meaning was added to the term polyphony with the introduction of music synthesizers. Early synthesizers were only able to sound one note at a time. More modern music synthesizers are able to play multiple musical notes concurrently. Those synthesizers were then referred to as "polyphonic."

This is a slightly different meaning for the term, and created a bit of confusion.

The semantic situation became even more confusing with the introduction of ringtones for mobile phones.

In the context of mobile phones, a "polyphonic ringtone" is a ringtone in a file format which supports multiple concurrent notes and where the notes are generated by the telephone itself.

A ringtone with just one note at a time and which is generated on the phone is a "monophonic ringtone."

The notes in MP3's ringtones are not generated on the mobile phones, but are instead digitally sampled recordings which the phone merely plays back.

Most polyphonic ringtones are stored in MIDI format (MIDI, MIDI 0, or SP-MIDI). Sagem 2.1 and Qualcomm CMX versions 1 and 2 also support polyphonic ringtones.