The logical deduction to the answer is "YES". How many stenographer, should be more than one, but one contributed the most, another were supplementary.
The earliest evidence of written materials existed amongst the Israelite was seen in Deu 31:9-11 (NIV)
9 So Moses wrote down this law and gave it to the Levitical priests, who carried the ark of the covenant of the Lord, and to all the elders of Israel. 10 Then Moses commanded them: “At the end of every seven years, in the year for canceling debts, during the Festival of Tabernacles, 11 when all Israel comes to appear before the Lord your God at the place he will choose, you shall read this law before them in their hearing.
The purpose of it was "so they can listen and learn to fear the Lord your God and follow carefully all the words of this law." Deu 31:12(NIV)
With the same principle, the gospel will be preaching with expectation for the next thousands of year, it must be in written. But God did this differently. We may notice that God intervention was getting more subtle when human is getting more civilized. It should be well understood as we believe God by faith, "Now faith is confidence in what we hope for and assurance about what we do not see"(Hebrew 11:1 NIV). Jesus chose His disciples on purpose that His disciples didn't even know their specific function in His plan.
Who was the main stenographer? I believe that he was Matthew. As many scholars pointed out, Matthew was a tax collector that had a practice of recording, and he wrote the first Gospel. I notice also, in all four gospel, his name was rarely seen except when the names of the 12 disciples were mentioned. He looked like a bystander. The gospel of Matthew is well conceived as the best gospel for disciple training. The Five Discourses of Matthew; the Sermon on the Mount, the Mission Discourse, the Parabolic Discourse, the Discourse on the Church, and the Discourse on End Times. These comprehensive discourses were not possibly pieced together if not well digested by first hand person.
The Gospel of Matthew has the most record of Jesus teachings, parables and miracles. The Gospel of Luke has the second most but Luke was not a disciple of Jesus, he participated in Paul missionary around 16 years after Jesus had crucified on the cross, however, the Gospel of Luke discloses some new materials that are not in Matthew. From his introduction (Luke 1:1-4, the title question), he clearly mentioned, he was not an eyewitness but he had been carefully investigated the eyewitnesses and servants of the word. What being said was Luke required multiple persons to confirm the same thing, before he trusted on the account.
Matthew might have based on his own resources. But Luke sources should be a lot more extensive. Amongst the most new sources in Luke that were not in Matthew, most were the parables, such as the good Samaritan, the prodigal son, the shrewd manager, the rich man and Lazarus. Some might seem to be a variation, such as the great banquet.
I believe the writers of the Gospel and the Epistles that eventually formed the New Testament had never been conceived their influence to their future world. But it is a very logical deduction that early written materials are essential, for it provided the first person narrative of Jesus, similar to the Pentateuch that God proclaimed His commandments.