Music Theory/Playing by Ear

Playing by ear is both inherently difficult and inherently easy due to two things:

1. The music is played as heard — therefore, rhythmic values and expression are easier to pick up and replicate in one's own playing.
2. The music is, more often than not, unknown as a piece to play to whomever is playing it, and as a consequence he or she, depending on the attention to which they feel inclined to play the piece, will have to work out key, chord changes, melody, harmony and technicalities like fingering on their own.

Some people have a gift known as perfect pitch, that is, they are able to tell from listening to a specific note or chord what it is. This may aid them immensely when they try to transcribe a piece of music or play it by ear.

The best way to learn to play by ear is to first develop your ear, that is, play easy songs without notation. Play along to the song, so you know you are in the right key and always use an instrument that is in tune (if applicable). If you are blessed with a particularly good memory, you will be able to memorize songs and chord changes without too much difficulty. This gift does not have a name, but is comparable to perfect pitch in its use and applications. Playing songs in one's head in the right key is not difficult after some ear development, so play by ear when you don't have notation.

Not all people have the gift of perfect pitch, but one skill that you can develop is the ability to recognize relative pitch. That is, being able to tell what a note is by relating it to a reference note, or being able to tell what a specific chord is by correctly hearing the relative intervals between the notes within the chord. This ability would be a more useful tool for learning to play any song in any key. For example, you hear the first three notes of the melody of a certain song. Although you would not be able to exactly pinpoint what the actual notes are, you would still be able to duplicate what you heard (but perhaps not in the original key) by identifying the intervals between those three notes.

Learning this skill means learning to play, and more importantly, hear the different intervals between notes: unison, minor 2nd, major 2nd, minor 3rd, major 3rd, perfect 4th, and so on.