Double bass drum technique is a combination of thigh and ankle muscle movements that I recommend playing heel up. The chart for this lesson looks insane but is easy to understand when looking at the bass drums as broken triplets. The first note of every triplet is held in place by the snare drum as a ghost note and the second and third notes are played on the bass drum every time. This can be played in any time signature in duple and triple. This triplet figure played between the snare and kick creates a flurry of notes that are played in fixed frame. When hearing this lesson as a duple chant in 13, placement of triplets are easier to grasp. Tempo variations become smoother with repetition.
The focus here is the beginning look into double bass drum techniques. Drum throne height is a factor. There is such a thing as right handed and left handed double bass playing, meaning which foot begins the phrase or phrases. In my case being predominantly right handed (I hold a pen and fork with my left hand), I execute double bass beginning with my left foot. Foot placement on the pedal board is also demonstrated along with other techniques.