gistfile1.txt

var bandSchema = new mongoose.Schema({
  name: String,
  lead: { type: mongoose.Schema.Types.ObjectId, ref: 'person' }
});

var autoPopulateLead = function(next) {
  this.populate('lead');
  next();
};

bandSchema.
  pre('findOne', autoPopulateLead).
  pre('find', autoPopulateLead);

var Band = mongoose.model('band', bandSchema, 'bands');

Why don't you pass next as second parameter of this.populate('lead'); (L7)?