Music is known for its ability to express as well as to evoke emotions. However, there is very little scientific research on what means musicians use in their performance to bring about different emotional expressions. In a series of ongoing experiments musicians are asked, using various instruments (violin, flute, electric guitar, synthesizer, singing voice), to perform short monophonic pieces of music to have them express ``happiness,'' ``sadness,'' ``anger,'' ``fear,'' ``solemnity,'' ``tenderness,'' and ``no expression.'' Listening experiments are conducted to confirm that listeners recognize the intended emotions. Approved performances are analyzed using sampling systems. The intended expressions affect practically all physical variables---tempo, timing of various units, articulation, sound level, amplitude envelopes, intonation, spectrum, onsets and decays, vibrato---in ways that differ among expressions and instruments used. There is considerable interindividual variation among performers in their ability to render the intended expressions as well as regarding the means that they use to achieve the expressions. On the other hand, listeners differ in their ability to recognize the intended expressions. Some emotions seem easier to express as well as to recognize than others.