The bass is the most important instrument most listeners never consciously hear. Take it out of a mix and the record collapses: the low end goes, the groove loses its weight, and the harmony becomes ambiguous. A bassline does two jobs at once - it locks with the drums, and it tells the ear what chord is underneath.
The mechanics: which notes to play
Every note in a bassline belongs to one of four families. Knowing which is which is the difference between a bassline and a series of low notes.
- Root notes - the note the chord is named after. The safest choice, and the strongest. On the first beat of a new chord, the root is almost always right.
- Chord tones - the third and fifth (and seventh, in a seventh chord). They outline the chord while adding movement. Root-fifth-octave is the backbone of country, rock and a great deal of dance music.
- Scale tones - other notes from the key that are not in the current chord. Used on weaker beats, they connect one chord tone to the next.
- Chromatic and passing tones - notes from outside the key, used briefly to approach a target note from a semitone above or below. A chromatic walk-up into the next chord is one of the most recognisable sounds in funk, Motown and jazz.
The general rule: strong beats get chord tones, weak beats can travel. Land on the root or another chord tone when the chord changes, and use scale and chromatic notes to get there.
Types of bassline
- Root notes on the beat - simple, powerful, leaves space for everything else. Punk, much pop, much dance music.
- Root and octave - the disco bass: an octave jump on every off-beat.
- Riff-based - a repeated melodic figure that becomes a hook in its own right. Often the most memorable part of the song.
- Walking bass - a note on every beat, moving through chord and scale tones with chromatic approaches. Jazz, swing, rockabilly.
- Syncopated 16th-note lines - funk and modern pop, locked tightly to the kick and hi-hat with ghost notes and rests.
- Sustained and sub bass - long notes or 808s, more about weight than movement. Trap, drill, much electronic music.
- Pedal bass - one note held or repeated while the chords change above it, building tension.
Lock with the kick
The kick and the bass occupy the same frequency range and the same rhythmic role. The cleanest grooves make a decision about how they relate.
- Unison - bass notes land with the kick. Punchy and tight.
- Interlocking - bass plays in the gaps between kicks. Busier, funkier, but each part stays clear.
- Long against short - a sustained bass under a short kick, with sidechain compression ducking the bass when the kick hits.
Write the bassline with the drums playing. A line that sounds great on its own often clashes with the kick.
Playing styles
A real bassist sounds different depending on how they strike the string, and your programmed part should reflect a choice.
- Fingerstyle - warm and round, with a soft attack. The default for soul, Motown, much pop.
- Pick - brighter, more attack, more definition in a dense mix. Rock, punk, some funk.
- Slap and pop - the thumb slapping the low strings and the fingers popping the high ones. Percussive, aggressive, bright. Late-70s and 80s funk, and very easy to overdo.
- Muted - palm or felt muting for short, thuddy notes. Classic in 60s and 70s soul.
Choose an instrument patch that matches the style, and write parts a player in that style would play.
Programming a sampled bass
Good bass libraries - Native Instruments' Scarbee series and similar - give you the articulations a bassist uses. Learning them is what makes a programmed part convincing.
- Keyswitches. Most libraries use notes below the playable range to switch articulation. Check the manual; positions vary between libraries.
- Legato and hammer-ons. Overlapping two notes usually triggers a hammer-on or pull-off instead of a new pluck - a smooth connection rather than a fresh attack.
- Slides. Many libraries slide between overlapping notes a larger interval apart, or slide when you play with a particular keyswitch or controller.
- Harmonics are often mapped to very low velocities. Keep your normal notes above that range or you will trigger them by accident.
- Mutes and release noises. Muted notes, finger noise and string release sounds are what make a part sound handled. Use them at the ends of phrases.
- Sustain pedal (MIDI CC64) in some libraries lets notes ring into each other or triggers different behaviour - check what yours does.
- Fret position. Some libraries choose which string a note is played on; others let you force a position. The same note on a thicker string sounds darker.
Above all, write within the instrument. A four-string bass in standard tuning goes down to the E below the bass clef. If your line goes lower, either the player has a five-string or the part is unrealistic.
Mixing and sound design
- Two jobs, two bands. The low end (roughly 40-100 Hz) carries weight; the upper mids (roughly 700 Hz-2 kHz) carry definition, so the bass is audible on small speakers. If it disappears on a phone, add or emphasise the upper harmonics - with EQ, saturation or a distortion layer.
- Compress for consistency. Real bass notes vary in level; gentle compression evens them out so the low end feels steady.
- Give the kick room. Sidechain, EQ carving, or simply an arrangement that keeps them from fighting.
- Mono below about 100 Hz. Low frequencies spread across the stereo field lose power and cause trouble on club systems and vinyl.
Do this now
- Take a four-chord progression and write a bassline using only roots on beat one.
- Write a second version that adds chord tones (thirds and fifths) on other beats.
- Write a third that approaches each new chord from a semitone below on the last 8th note of the bar.
- Program the third version with a sampled bass, using legato for at least one hammer-on and a muted note at the end of the phrase. Check it against the kick.