Once you can hear both parts cleanly and in HD in your head, it’s time to pick up the guitar. Don’t sing at this point though; you first need to make sure that you can execute the guitar part flawlessly, without thinking, and that you’re able to sing the vocal part without any hesitation. When you’re ready, play the guitar part and sing along in your head. Here’s where you need to balance out your attention as at first it’ll waver between the two. The good thing is that now you have the recording imprinted on your brain as a reference, which should help you iron out any syncing problems. Play through the song a few times and observe how your attention settles into a kind of mid-point where it’s not focusing on either part. I recommend spending a good amount of time on this stage, in fact, the more time you spend on this stage; the easier it’ll be when you try to sing it out loud.
When you start to feel confident you can sing it out loud, go for it! Although the result may not be perfect, I think you’ll be pleasantly surprised at the drastic improvement made in this area, and you’ll definitely have something to work with. If there wasn’t a marked improvement in your singing and playing, go back and repeat the first two steps; these are the critical ones. If you find your attention wavering to either part it means that you need to go over them again until they become second nature.
The most important thing is not to rush this process, and if you get frustrated, leave it for a while and come back to it later as the brain often needs time to process things. Good luck!
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