I started out as a classically trained guitarist and spent my high school years playing bass in a (school) jazz ensemble, so I have some (limited) formal musical training. Playing rhythm in Jazz required me to be able to hold tempo/count/etc. do everything in order to not let down the ensemble, the years of berating by the director really beat that into me.
I've since moved to school and have (sadly) been missing ensemble playing for 3 years. However, recently I've been getting together to playing some rock/folk music with some friends, we are semi-serious and have had several gigs at local events. They are all great musicians in their own right - but they do not know how to hold a tempo as an ensemble, and refuse to listen to their bass (since the drummer is also a self-taught rock guy) for rhythm cues. Frankly its the main thing holding back the group from sounding more professional.
I've tried everything I can think of - from turning my levels way up to force them to listen , to acting as a human metronome during rehearsals, with limited success - they listen during practice, but during a performance all hell breaks loose and they decide to suddenly double the tempo after a particularly moving solo. I was whooped every day by a conservatory trained Conductor with a PhD in music and a surprisingly short temper, combined with the fact that our drummer was essentially the best youth drummer on the west coast so I could always rely on him if I screwed up during a performance.
They are willing to learn, but how can I give them a crash course in rhythm and keeping tempo?