Baroque music was very profound in the way it used harmonic dissonance. Though dissonance might sound like something that composers would want to avoid, it is actually an incredibly important tool for producing emotion.

The stress of a note that doesn't fit a chord creates tension and the resolution to a more harmonious note releases that tension.

In Pachelbel's Canon, a famous piece based on a repeating chord progression (like a ground bass), the principal melody that comes in at 0'15 contains notes that all fit each of the chords (see notation below). This helps to produce a feeling of calm and contentment.

As more ideas get layered on top to make an increasingly polyphonic texture, some of these notes cause harmonic dissonance. For example, notice how the countermelody from 0'40 includes some notes which don't fit with the prevailing chord. There is an arrow above them on the notation below. These are very minor tensions which are often called passing notes because they move by step between two harmony notes.

At 3'20, a melody is introduced which includes even more passing notes. There are 8 of them within the chord progression. One of them is a C natural which sounds particularly discordant with the harmony of that beat.

Overall, the treatment of dissonance was something that Baroque composers were very careful with. Not too much and not too little. It took until the Romantic era for composers to become a bit more daring!

You could spend a long time highlighting every passing note in Bach's Brandenburg Concerto movement! Passing notes are important musical features and can often relate more to Melody than to Harmony.

There are some interesting suspensions which are worth pointing out. These are notes which are held on and "suspended" over the next chord to produce a harmonic clash, before being resolved by falling down a step in pitch.

From bar 114 (1'47), the solo violin plays a G# which is held on to the next beat to form a suspension. The tied notes form a whole string of suspensions which is particularly dissonant because the flute joins the violin with its high A a bar later, also producing a series of harmonic clashes. It is possible to hear the alternation between tension and resolution over the next few bars and this helps to drive the music forward with a lot of momentum.

There are many pedal notes which can be heard in the B section of this movement. From bar 79 (1'13), a throbbing quaver is heard on the downbeat of every bar emphasising the new key with a tonic pedal note. It helps to support the melody which is functioning in this new key.

A dominant pedal note is heard from bar 198 (3'07). It is more noticeable on the score because it is a sustained note in the bass. A dominant pedal sounds more unsettling because it makes the listener pine for a resolution to the tonic in a satisfying perfect cadence. Lingering on the dominant produces a sense of unease. Another can be heard in the key of B minor at bar 217 (3'25) which has a similar effect.

Though it is quite short, a pedal note is heard from the flute and violin at the top of the texture from bar 142 (2'14). This is subsequently called an inverted pedal.

Perfect cadences are really important for establishing the key in Bach's music and also for concluding a phrase in a very definite way. These include:

• Bars 77-78. A perfect (V-I) cadence in D major (A-D) which concludes the A section.

• Bars 147-148. A perfect (V-I) cadence in A major (E-A) which establishes a modulation.

• Bars 231-232. A perfect (V-I) cadence in B minor (E-A) which concludes the B section.

• Bars 309-301 (the end!). The use of a perfect cadence to conclude the whole piece in D major allows the piece to finish in a well-rounded manner.

Overall, the use of perfect cadences at the end of phrases is very typical of music from the Baroque era.