Video it, watch it with him, then e honest and tell him. He’s not only limiting the band but he’s limiting himself. Or Maybe it’s something he can fix. If his writing is great, he’s getting in his own way by not giving the song the justice it deserves. You might get run, but fuck it, why waste your time sucking if your band mate won’t get out of his own way.

2nd attempt to answer: Physical work will produce testosterone, also consider those in field that require physical activity may be subjected to random drug screenings, which may deter the likelihood of sperm reducing illicit drug use.