No, It wouldn't. It just makes him a Missing Nin, hes still a Leaf Ninja. Sasuke would only be a Sound Shinobi if he went and got a headband. Orochimaru isn't actually offically a Sound Shinobi, Kabuto still is, If you look closely at Orochimaru, he has no headband, but if you look closely at Kabuto, you'll see a sound shinobi headband, but its not scratched out, meaning hes still part of the sound.
If you know Oro's past, you'd know hes actually a Leaf ninja, seeming he lived there long before going to the sound, of course, he never truely joined the sound, he joined the Akatsuki, and left when Itachi wouldn't give him his body. Sasori, who was upset his partner had left him, sent Kabuto after him as a spy, secretly meeting with him when he could.
After awhile, Oro broke Sasori's Jutsu, and when Sakura, Sai, Naruto, and the sensi that was filling in for Kakashi-sensi went after the spy, Oro attacked, and Kabuto was on Oro's side, not Sasori's, even though it truely wasn't Sasori, because Sakura and Lady Chiyo killed him a few episiodes before that.
Of course, these could be some spoilers for you, If I spoiled anything for you, I am truely sorry.
~Dosu Uchiha:D
Sound ninja are the followers of Orochimaru just like leaf ninja- they live in the sound village that Orochimaru created. No one knows its exact location
Orochimaru isn't dead yet.
Sound Ninja
He and the other sound ninja fight Sasuke in episode 109 (An Invitation from the Sound).
Orochimaru probably came up with the idea.
He first leaves with the sound ninja five to join Orochimaru. Naruto and some other genin leave on a mission to find him, but Naruto gets the crap beaten out of him by Sasuke. Then in Shippuden Sasuke eventually kills Orochimaru and forms his own to team to hunt down Itachi Uchiha. Just watch the show on narutoget.com to watch what happens after, there's a long story.
I'm not sure if this is the answer you are looking for but I'll do my best. When Sasuke left the village he did join the Sound 5 however, they were all killed when trying to bring him to Orochimaru. This meant there was no more sound five. If your question is asking if he joined the Hidden Sound then no. Although he joined Orochimaru, he never wore a sound head band. Also keep in mind that Orochimaru basically used the sound to try and bring down Konoha before ditching the sound village when they failed.
In Konaha: Of course Team 7 Team 7: Naruto Uzumaki, Sakura Hanuro and Sasuke Uchiha. Sensei: Kakashi Hatake: Jounin Rank Ninja While leaving Konaha: Sound Four: Sakon and Ukon, Jirobo, Tayuya and Kidomaru Leader: Orochimaru
Okey, i will tell. its: orochimaru,kabuto,kidomaru,sakon,ukon,tayuya,jirobo,kimimaru,juugo,karin,sasuke,guuren,yuukimaru,other nameless ninja from the sound village the ones who ware black and white i think there are nine of them,zaku,touchi,and that mummy guy from the chunnin exams... well, i think that's the last of em..
The Sound Four (along with there leader). Sound Four Members: Sakon and Ukon (share one body), Jirobo, Kidomaru, and Tayuya. Leader of Sound Four: Kimimaro
Naruto Episode 33
Sasuke leaves Konoha because he wants more power to be able to kill his older brother Uchiha Itachi. He believes that if he goes to Orochimaru in the Otogakure (Sound Village) that he will obtain that power.