Modulation is the process of moving from one key to another key, in contrast to transposition, which means to play a song in a different key.
People tend to get those two word confused, because if you're playing in one key and then transpose the music to a different key, you have to modulate to get to the new key.
So the key is simply to get to the V7 chord of the new key as smoothly as possible. I often play the ii of the new key before the V7 to make it smoother. Lets say your in the key of C Major and want to move to A Major key. You play C chord, F chord and G chord then go back to the C chord in the key of C then play Bmin7, E7 and then onto A and your now in the A key. Try it it sounds good.
More to come...
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