Understanding and Improving Kick Drum Technique

For over eight years, my brother and I have enjoyed playing and writing music together. As I strum chords and pick an array of notes on the fretboard of my guitar, my brother is working tirelessly behind the drum set. As he is a true hard rock/metal drummer, it always amazed me how quickly he could play the kick drum with his feet. 

Not only do drummers like my brother have to keep a fast tempo throughout the song, but they have to play complicated rhythms with their feet using a double kick drum pedal (shown below). Each hit of the kick drum should strike the drum with a significant and similar impact compared to other hits; playing the kick drum too quietly loses its punchy sound, and this is particularly noticeable while playing quickly as softer hits become difficult to distinguish. 

(Image of a double kick drum pedal)

The force exerted on the kick pedal by the drummer should ideally be the same between hits. As the beater (the circular piece that makes contact with the drum) strikes the kick drum, it exerts a force on the head of the kick drum. By Newton’s third law, the drum head exerts an equal and opposite force on the beater. The equation for force is shown below: 

F = ma

Here I ignore the force of friction and assume that all kinetic energy is transferred from the pedal into the beater that strikes the kick drum (therefore treated as the same direction of motion). The mass of the drummer’s foot and leg also remain the same. Therefore, in order to hit the drum with the same force, the acceleration of the beater, and therefore the acceleration of the drummer’s foot and leg, must be the same between hits. To calculate the work done on the kick drum by the beater, the equation for work can be used as illustrated below: 

W = F||d

Because the displacement of the beater remains constant, the force exerted by the beater is directly proportional to the work done on the drum head. The net work is equal to the change in kinetic energy as shown below:

Wnet = delta KE = 1/2m(vf^2-vo^2)

Similarly, in order to do the same amount of work on the kick drum, the final velocity of the beater must be the same given that the initial velocity is always zero (resting position of the beater). 

To connect these ideas together and translate them into a practical application, we need to investigate the nature of acceleration, which is shown below:

a = delta v/delta t  

As already established, in order to exert the same force and do the same work on the kick drum to maintain a pleasant and punchy sound, the acceleration and change in velocity must be equivalent between hits. Therefore, the drummer must extend their legs in the same time interval to maintain a steady acceleration with the same change in velocity. This becomes particularly challenging while playing quickly. If the drummer's legs extend more slowly, the acceleration will decrease and less force will be exerted on the kick drum, making a quieter sound. This decrease in force translates to less work done on the drum head, also corresponding to a slower final velocity of the drum beater. Consequently, as more experienced drummers practice and improve their kick drum technique, they are able to increase the rate at which they can return their foot and leg to rest position after striking the kick drum. This permits drummers to strike the kick pedal with a near-maximal force for each hit in rapid succession. Using this information, if drummers notice that their kick drum playing sounds inconsistent, their legs are not accelerating at the same rate between hits. They should work to strengthen their muscles to increase the acceleration of the pedal and kick beater while improving the time they can return their legs to rest position, allowing them to exert a similar force shortly after striking the kick drum.