Hi, I play a PSR S970, I record the song in midi form on the USB clip, that way it doesn't take up much memory.
If performing live you can then replay that recorded song as a backing song & sing along with it & add any extra right hand sounds you wish.
Or, if you just want a total recording of keys plus voice you can play the recorded song into a DAW [eg Bandlab's Cakewalk Pro - it's free & pro standard with lots of tutorials on YouTube] = I record the backing onto 2 tracks, 1 left & 1 right; I then record the vocals onto a third track, with backing vocals onto a 4th track if required.
You need a box to connect between your keyboard [& mic] and the computer - I use Focusrite Clarett 4 pre USB as it has 2 headphone jacks each with a volume control - great for duo recording.
Hope this helps,
Mike