AudioNodes has a powerful concept of working with melodies and MIDI data: dedicated melody inputs, outputs, and connections.
Melody connections are visualized with green, and transmit either pre-composed, or live melody data from one Node to another. These are technically different from (and incompatible with) audio and control inputs: while those transmit a single real-time value (one audio or control sample at a time), a melody connection transmits the entire melody data, with unlimited polyphony.
There is a separate set of Nodes for working with melodies, and you’ll always begin with a melody source Node, then connect that either to a melody-controllable audio source Node directly, or to Nodes that perform further processing on melodies (such as automatic chord generation).
The next article will show you how to set up a melody source.