Hi,
Make sure your instrument (Yamaha PSR-A3000) is switched to the right mode, please. There are modes like Combi, Multi, Song, Patch, Voice, or something like this. Check you hardware manual to double-check, which Mode should be selected, if you want to use your hardware with multi-timbral option.
My guess is, you are using some kind of Combo (or Multi) sound on your hardware. These sounds layering the sound by using multiple MIDI Channels.