Pitches played on familiar instruments are fairly well-defined. Now put down the instrument and play the pitches in your head; gets interesting. For example, m

Pitches played on familiar instruments are fairly well-defined. Now put down the instrument and play the pitches in your head; gets interesting. For example, make up a simple tonal melody 'in your head' and 'play' it for a minute. Now try to 'play' the melody in the key a half-step higher. Not always so easy!