A piece of music is often only as good as its bass line. The most memorable part of a tune from classic songs by artists like Masters at Work, Michael Jackson, or more recently the Black Eyed Peas would be so much less without the groove that’s driven by a good beat and a great bass. In this article, we look at some common chord structures and methods of creating a good bass line that will help to create better bass in your music.

In order to understand the process behind writing a good bass line, we need to know some basic scales and chords. The two basic forms of musical scales are Major and Minor. The major has a more ‘straight’ sound, while the minor will usually set up a more melancholy or darker sound. Don’t be fooled into thinking that all songs in a minor key are dark and brooding, though, as the ‘black’ notes used at the appropriate times are what makes the difference between something really ordinary and a tune that has the right edge to make a really great piece of music. The C-major scale is C-D-E-F-G-A-B-C, which is of the form Tone-Tone-Semitone-Tone-Tone-Tone-Semitone. The C-minor scale is C-D-Eb-F-G-Ab-B-C, which is of the form Tone-Semitone-Tone-Tone-Semitone-Third-Semitone.

The most common of all rock bass lines is often referred to as the 1-4-5 progression. These numbers are a reference to the first, fourth and fifth notes of the scale that the song is based on. If we spaced the notes at regular intervals, a good example would be something like 1-1-1-1-4-4-5-5, with the corresponding notes C, F, and G. Two examples of this bass progression are in Example 1 with a kind of jazzy feel to it. Any combination of notes and rhythm could be used and would give very different results. The same 1-4-5 progression is in Example 2 with more of a straight rock feel.

The bass line must fit in with the chord progression of the song. In the examples above, this type of bass line will work for any number of styles of music. Other bass lines are the walking bass found in house tracks, the syncopated bass in hard house or NRG tracks, or the weird and wonderful bass lines in the more techie tunes. See Example 3 for a disco walking bass example.

A seventh chord is a chord or triad that has a note the seventh above the tonic in it. The seventh can be used as a kind of bridging chord, which ‘destabilises’ the triad and allows the writer to progress into something different by raising or lowering into the next chord progression. There are many types of seventh chords, depending on the type of triad and the quality of the seventh. An example of this is that a chord consisting of a major triad and a minor seventh above the root is referred to as a "major/minor seventh chord, which is usually referred to as the dominant seventh." Of the eight possible constructions of seventh chords using major and minor thirds, the five most common chords are detailed below:

• Major Seventh – root, major third, perfect fifth, major seventh (e.g. F-A-C-E)
• Minor Seventh – root, minor third, perfect fifth, minor seventh (e.g. F-A b-C-Eb)
• Dominant Seventh – root, major third, perfect fifth, minor seventh (e.g. F-A-C-Eb)
• Half Diminished Seventh (a.k.a. “seventh, flat five” among jazz musicians) –root, minor third, diminished fifth, minor seventh (F-A b-B-Eb)
• Fully Diminished Seventh – root, minor third, diminished fifth, diminished seventh (sixth) (e.g. F-Ab-B-D)
  

The dominant seventh is the most common of all the sevenths, as it is simply the first, third, fifth and seventh notes of the given scale. The dominant seventh chord is useful to composers because of the fact that it is a major chord with a very strong sound. The third of the chord is the leading tone of the scale, which has a strong tendency to pull towards the tonal centre, or root note, of the key. In the example of an F-Maj7th (F-A-C-E) it is unclear when listening whether the chord being played is an F-major (F-A-C) or A-minor (A-C-E). This is a very important usage of the dominant seventh chord, as it offers a seamless transition to the new key. In this context, a nice jazzy bass line works well, and the arrangements can be made by simply experimenting with the rhythmic arrangement and structure of the 1st, 3rd, 4 th, 5th and 7th notes of the scale.

The bass line needs to balance the harmonics of the key the song is in. If the key is G-Major, for example, a good rule of thumb is to put the root, which in this case is G, on the downbeat (i.e. the first beat of the measure). That helps define the tonality and maintain the theme of the song, as mentioned earlier. B and D, as the third and fifth respectively, are the strong chord tones. After the root, these are arguably the most important notes to consider in building a line. The A, E and F#, as the second, sixth and seventh respectively, are less important for defining the "G-ness" of your line but can provide a lot of colour and interest and should not be overlooked. If the key is G7th instead, the only difference is that there is an F natural rather than F#. In this situation it is usually best to play the F below the G rather than just going up the octave.

If there was one governing rule for a good bass line, I think simpler is often much more effective. This of course doesn’t always apply, especially for some really clever bass lines, but I think you will know when you’ve ‘made it’ when you reach the point when the music you think sounds good actually sounds good to other people as well. It’s fascinating, and often eye-opening, how simple the chord progression for a song is. A lot of the most successful songs of all time are just simple chord progressions based on a formula long-proven and it just plain works.

Quick definitions:

• A triad is a chord based on the first, third and fifth notes of the given scale.
• The tonic is the root note of the scale.
• A diminished chord is one made up entirely of minor third intervals - 1.5 notes away from each other

 References:

• Seventh Chord
• More on the Seventh Chord
• Walking Bass Lines
• Bass line Tutorials
  

Music:

The sample MP3 contains the following examples

• Example 1: 1-4-5 jazzy bass line
• Example 2: 1-4-5 rocky bass line
• Example 3: Disco walking bass line
• Example 4: Minor-2 bass line
• Example 5: Minor-2 bass line