General Outline:

Very influenced by jazz melodies and harmonies, the 
bossa nova is played like a "soft" samba, with a 
simplified rhythmic section, and more elaborated 
harmonies.

From the south east of Brasil, more specifically Rio de 
Janeiro, the bossa nova reached its apogee in the late 
fifties and is more well known internationally than most 
forms of Brasilian music.

Antonio Carlos Jobim (as composer) and Joao Gilberto 
(primarily as a singer and guitarist) are the most 
important artists in bossa nova. Their first important 
recording was "Chega de Saudade" (March 1959).

Musical Characteristics:

Certain harmonic progression have almoust became 
"cliches" since the advent of the bossa nova, such as 
the shifting of major and minor modes in a tonic-
dominant relationship (e.g. Gm7 to Cmaj7) and 
harmonic substructions for the classic II - V - Im using 
minor 6 and diminished chords.

Example 1 is a diatonic harmonisation.

Examples 2 -- 5 is a "bossa nova" style 
reharmonizations.

In the rhythmic section we will usually find small groups 
with soft percussion instruments (claves, match box, 
tambourine, ganza).

Bossa Nova clave:

The "clave" is a rhythmic "cell" that's the root of most 
rhytmic patterns. This "cell" is usually played all the 
way through a song by a percussion instrument knows 
as "claves" (two round polished sticks which are 
struck together), or any other instrument. On the drum 
set, it can be imitated by the rim shot.

The "clave" can be played as shown on Example 6 or 
inverted (Example 7), but once the pattern begins, it 
doesn't revert.