You will need some form of software library, or need to use MS' DirectSound, to create, and playback, sounds in C# WinForms.
NAudio is open-source, very powerful, on CodePlex, can be installed in Visual Studio using NuGet, and has a discussion Forum that is active: [
^].
Or, you could use DirectX Sound, and use System.Media for playback; here's a well documented example (with source code) of how to creates, and play, a sine wave: [
^].
Do search on CodeProject, because I am sure there are some DirectSound examples here.