One of the most frustrating things to do when you are learning to play by ear is finding the key, then finding the chords to a song. Although a song can seem easy, it is not always easy finding the key. This page addresses 2 methods that you can use to find the key to a song:
Method 1 (Standard)
The first method to finding the key is by identifying the Tonic. Here is how you find the key using the Tonic method:
Key Idea #1
If you haven't memorized your scales, intervals, and triads using relative pitch, try and find the tonic by humming the main note and build the scale from there
Method 2 (Advanced)
The strategy to finding the key to a song if you already know your scales is different then if you do not know your scales. But before you can use the more “powerful” method to finding the key to a song, you must know two these:
1) Know your major scales
2) Know your diatonic triads
Many musicians think they know their scales, or triads only because they can play them. But “knowing” triads means, knowing how they SOUND. Knowing how they FEEL. And this is what trips many beginning musicians.
You cannot treat music like a mathematics. Yes, music requires head knowledge, but it also requires intuition, feeling, a sense of how parts relate to a whole, and the ability to listen and perceive...
If you know your scales and triads by intuition and by sound, then you will be able to tell, by listening, the difference between a 4th and 4th degree triad.
In fact, you can get so good at determining the distance of triads (called relative pitch), that even without perfect pitch you can know both the key and the chords to a song, simply by listening to the patterns.
Question: What patterns should I to listen to?
Listen for how certain chords resolve?
Listen for 5-1 progressions to establish a key
Listen for how certain chords or patterns repeat?
Listen for the bass note?
A person with an amazing ear can listen to all these things and determine a key, oftentimes, within seconds.
But this takes, practice, patience, and persistence.
See the video below for a thorough explanation on this
Key Idea #2
If you know your scales, intervals, and triads using relative pitch, listen to how the chords resolve to find the tonic chord