Modern music as we know it today is almost always recorded, stored, and distributed in the form of waveforms of audio. Whether that is a waveform recorded from a microphone, keyboard, or sampled from pre-existing audio recordings, they ultimately all get stored and distributed as a seamless wave of music. They can be stored in a digital format like MP3's and CDs, or in an analog form like the physical grooves on a vinyl record. In either case, it is a recording of audio, that when sent through your audio amplifier, tells your speaker how to move in order to reproduce the song accurately.