In reply to Donny's question in another thread I thought it wise to start a new one as the subject is different.
This is how I have proceeded over the last few weeks Donny:

Requirements:
1. arranger keyboard or other instrument.
2. Audio interface ( e.g. Steinberg, Behringer, Focusrite)
3. DAW, in this instance MIXCRAFT 9PRO
4. decent and fast computer, desktop or laptop
5. Recent smartphone e.g. Samsung S,6,7,8,9,10 or Tablet.

How to proceed:
1
get your keyboard ready to record song X
2
get your smartphone ready to start filming song X
3
Start both ,either simultaneously if someone is at hand or first the video and then the audio. Recommended to do a vocal
count in for later ( 4,3,2,1....).
The Audio is being recorded via the sound interface into MIXCRAFT on tracks 1 and 2. ( full PAN, left and right)
4
Do your thing
5
Store the video (probably an mp4 file) on your smartphone.
Transfer the video to your computer or laptop , if possible by cable, if not send yourself an email via Wetransfer.
6
In Mixcraft add a Video Track then add the Video to this video track.
7.Now SYNCHRONIZE the sounds of the audio tracks with the sound of the video track. Once that is done MUTE the sound of the video track and proceed to: Mixdown as.......
Mix it down as an mp4 ( or avi) track and the deed is done !!

Obviously you can still alter lots of stuff once you have done the above and befor mixing it down as a complete final video,but anyone using Mixcraft will know that......

Instead of using a two track audio recording you could opt for a three track recording ( provided you have a four track audio interface like my Behringer 404) in which you lead the vocal tracks seperately. Advantage being you can afterwards adjust the balance between keyboard and vocals as well as fine tuning the vocals with EQ, reverb, etc.

Hope this makes sense,

regards
John

Buy the Kodak for less than 50 bucks, plug in audio, push record and you have everything.