This seems to be a repenting man, a sinner. He (hence "when an innocent man sings") has commited some sort of crime. Quite possibly he could be in jail, or the "hole deprived of light" could be a pessimistic reference to world.
He wants to turn to the Lord in his time of need, but knows that he must atone for his sins, so he wants Him to "help me do thy bidding".
This seems to be a repenting man, a sinner. He (hence "when an innocent man sings") has commited some sort of crime. Quite possibly he could be in jail, or the "hole deprived of light" could be a pessimistic reference to world. He wants to turn to the Lord in his time of need, but knows that he must atone for his sins, so he wants Him to "help me do thy bidding".