Major 3rds Playing by Ear – Up 1 2 Now we will learn to play Major 3rds by ear on your instrument. By itself, a Major 3rd typically has a somewhat happy sound.November 27, 2012 1 2 Now we will learn to play Major 3rds by ear on your instrument. By itself, a Major 3rd typically has a somewhat happy sound. Major 3rd – Up Please press the Exercise button below.