The P-45 includes a USB-To-Host port; this can be connected to Mac computers, iOS devices and Windows PCs and will send and receive MIDI information once a connection is established.
So, for instance you could:
- Connect the P-45 to Cubase or Logic on a Mac, record yourself playing and play back the recording through the P-45
- Connect the P-45 to a virtual instrument on a Mac, iOS device or PC and use the P-45's keys to trigger the notes of the virtual instrument (and if the virtual instrument is running within a host recorder, record it and later export it as an audio file)
The USB connection doesn't carry the actual sound of the piano - only information about the notes that you're playing (and how you're using the pedal etc).
To record the actual sound of the P-45 (as you hear from its speakers or through headphones), you'd need to connect the P-45's PHONES/OUTPUT socket to a stereo input on a recorder of some type. This could be a handheld device (something like a Zoom H1) or a computer, tablet or phone with a stereo input (or better, a dedicated audio interface).
Please be aware that connecting a cable to the PHONES/OUTPUT socket will mute the onboard speakers (and so you may need to connect external speakers to the audio interface or device you're using, in order to hear yourself play).