Aggregate function isn't showing results with a count greater than 1

You should not add 'count': { '$gt': 1 } in the first $match stage.

As the count field is only populated after the $group stage.

So, you need add another $match stage after $group stage for filtering document with the count value is greater than 1.

db.collection.aggregate([
  {
    "$match": {
      "is_song": 1,
      "is_soundtrack": 0
    }
  },
  {
    "$group": {
      "_id": {
        "name": "$name",
        "artist_id": "$artist_id"
      },
      "count": {
        "$sum": 1
      }
    }
  },
  {
    $match: {
      "count": {
        "$gt": 1
      }
    }
  },
  {
    "$sort": {
      "count": -1
    }
  }
])

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