A bassline is usually one note at a time in the left hand, and most of its job is to say where each chord is. This section starts with roots on the beat and builds up through octaves, fifths and approach notes to improvising a line that still lands where it should.
Start this section in the interactive courseThe simplest bassline plays the root of each chord as the chord changes. Over Am F C G that’s A, F, C and G.
Use the left hand, low down: the octave below middle C is a good place on most keyboards. Left-hand fingers are numbered the same way, thumb 1 to little finger 5.
In these exercises the backing plays drums and chords but no bass. You’re the bass.
Alternate the root with the same note an octave up and a static root starts to move. It’s the classic disco and house bassline.
The hand makes an octave stretch: finger 5 on the low note, the thumb on the high one. Keep the shape and move it as one piece when the chord changes.
Play the low note slightly stronger than the high one; the line bounces instead of sounding flat.
The fifth (7 semitones up) is in every major and minor chord, so it’s safe against anything the chord does. Root and fifth together give a line shape without any risk.
A common pattern: root on beat 1, fifth on the offbeat of beat 2, root again on beat 3, fifth on the last offbeat.
The fifth below the root (5 semitones down) works as well and keeps the line low.
An approach note leads into the next chord’s root from a semitone below or a step above, just before the change. It makes the line sound as if it knows where it’s going.
The semitone below is the strongest pull. It’s often outside the key, which is fine: it only lasts a 16th or an 8th and resolves straight away.
Put it on the last step or two of the bar, so the root lands on step 1 of the next bar.
Many mono synths have a legato or fingered-glide mode: they only glide (portamento) and skip the new attack when a note starts while the previous one is still held. Playing that way is legato: press the next key before letting go of the last one.
On a sequencer it’s a tie or a slide flag. By hand it’s a small overlap: both keys down for a moment, then release the old one.
Try it on a synth with glide on and the legato setting active, and the line slides between notes only where you overlap them.
An improvised bassline has one rule worth keeping: be on the root when the chord changes. Between changes, use the minor pentatonic of the key and anything from this section.
Leave space. Bass parts with gaps let the kick through and sound tighter than a line that never stops.