Raising the perceived loudness with a「limiter」
This is an effect that is included with any DAW,
and is imperative in completing a finished product.
「There are cases when the balance of the song will differ greatly before and after」
In order to prevent this, follow this step.
First, after completing Dr, BASS, Vo, apprx. 80% of your song,
try applying a「limiter」.
When doing so, the key is not to place too strong of a limiting effect on the track.
By placing a「limiter」on the track during the mixing process, you can make small edits with the end product in mind,
and MIX knowing how the sound will change after applying the limiter,
helping prevent the sound from changing too drastically after a limiter is added.
Try this out if you are facing any of the problems above.
How sound pressure works and how to raise it
Explanation starts at 3:04