Playing an instrument by ear is a really great skill to have. It's the act of playing a piece of music without any written score. You can accomplish this by trial and error, or using specific techniques and thought processes. It's something which I've been developing over a few years, and in this article I'll introduce you to some of the ways in which you can try to play by ear.
1. Find The First Note
When I work out how to play a piece by ear, I start by either trying to find the first note of the song, or a common note which I can go back to. The way that I find that note is by playing the song and moving up the chromatic scale until I reach a note which sounds correct.
Once you've found that note, you can move onto finding the next note. Luckily, in many pieces and in many pop songs, the following notes are not too far away. This means that it's almost always very easy to work out the melody for a song.
2. Find a Chord
You should now try and work out a chord, probably the one which fits with the key signature. One way I like to do this is by playing some bass notes to find the root note of the chord, and then using trial and error to find out the remaining two or more notes. You could, of course, look online for the chords of the song you're wanting to play, but that'd be cheating!
Every other chord after the first one should be easier to find as they will tend to follow patterns throughout the song.
3. Add the Bass Notes
The first letter of a chord name, for example 'A minor', is also the note which sounds best being played in the bass part of the track. You could experiment a little here by either playing the same note in a lower octave to a higher octave constantly, or by playing the notes of the chord one at a time in the bass. Again, trial and error will be necessary to find out what sounds best.
4. Tweak the Sound
By now, you should have a melody, some chords, and a bass line. This may sound great, or quite dreadful! You can simply experiment at this point by changing the parts around slightly, or improving each section individually.
You could try to incorporate the chords and the melody together into one part by playing the note name of the chord along with the melody, though on some instruments, this may be quite a stretch.
Overall, once you have successfully combined all the different parts together, you should have a really great sounding piece, all of which you've played by ear! At this point, you could perhaps record yourself and post a video online, or impress your friends with your newly developed skills.