When using my foot pedals to play bass, I've primarily been using them to specify the current chord. I'll play the same pedal on each downbeat, switching when the current chord changes. There are a lot of things you can do with this, but on a real bass you'd normally play some things that are much more complex.

Consider this traditional bass pattern:

• A bass note on every downbeat.
• Odd downbeats get the current chord.
• Even downbeats get either:
  • If you are staying on the current chord, the fifth.
  • If you are going to a new chord, a half step below the new chord.

Here's an example on piano:

Can we play this with just feet?

I have four pedals, two for my toes and two for my heels. Let's notate these as:

'|	Left toe
.|	Left heel
|.	Right heel
|'	Right toe

We can also play multiple pedals at once. For example:

:|	Left heel and toe
.|'	Left heel, right toe
.|.	Both heels
'|'	Both toes
|:	Right heel and toe

Here's how I have my pedals set, assuming I'm playing in C major. I'm going to use Arabic numerals instead of Roman numerals because I don't want to think about whether the corresponding chord would be major or minor right now.

.|	1	C
.|.	2	Dm
'|.	b3	Eb
|:	3	E
|.	4	F
.|'	b5	Gb
|'	5	G
'|'	b6	Ab
'|	6	Am
:|	7	B

This gives us everything but the b2 (Db) and b7 (Bb), which I rarely play on bass when in major (for mixolydian I'd act as if the I was the V, which means the b7 is the IV).

The four one-pedal options are for the most common chords (I, IV, V, vi), while the six two-pedal options are for things you play less often. Ideally I won't need to add any three-pedal options!

This means we have everything we need to play that bass pattern over I, IV, V, and vi. For each chord we need three things: the root, the fifth, and a whole step below the root:

chord	root	fifth	flat root
I (C)	.|	|'	:|
IV (F)	|.	.|	|:
V (G)	|'	.|.	.|'
vi (Am)	'|	|:	'|'

That means this pattern would be:

.|   |' .|   |:
 C   G   C   E
  
 |. .|   |. :|
 F   C   F   B
  
.|   |' .|  .|'
 C   G   C   F#
  
 |' .|.  |' :|
 G   D   G   B
  
.|   |' .|   |:
 C   G   C   E
  
 |. .|   |. :|
 F   C   F   B
  
.|   |' .|  .|'
 C   F#  G   B
  
 |'
 C

Here's what this sounds like (it's on bass, so you may need headphones):

Eventually I want to play mandolin chords at the same time, but I'm not there yet.