Our drummer is not skillful in maintaining his tempo in a song. He starts out okay but somewhere down the line, he increases the tempo and drives the song out of the rhythm we are meant to have. He is committed. What do we do?
First of all, though his commitment is a plus, he needs to realize what the problem is. Get some songs for him to listen to and have him do a recording of himself replicating the tempo on his own. A replay of his own recording side by side of the original song will make him realize his weak spots. He is either rushing the song or dragging it.
There are websites for drummers to benefit from.
I recommend drummer world.com, libertyparkmusic.com, and learningjazzstandards.com among many others.
drummerworld.com has a discussion forum where someone asked a question about not being able to maintain a steady tempo. There are several responses that are helpful to your drummer. Many there recommended the use of a metronome that plays basic beats to help him identify his sore spots that need mending. A metronome is a device that produces an audible click or another sound at a regular interval that can be set by the user, typically in beats per minute. Some others talked about having self-control and an awareness of an inner clock, not being carried away by adrenaline. The diversity in opinions comes from their personal experiences which is a pool of useful information for any drummer.
While libertyparkmusic.com has an article on common mistakes made by beginner drummers and how to avoid them, learningjazzstandars.com talk about tempo versus time feel and tips on how to improve them.
The onus is on your drummer as well as on your concerned group members to help him have access to the information he needs for improvement.
However, as much as a drummer is the timekeeper of the group, other musicians and singers can distort the tempo.