With Bass you can do whatever you want. Some time ago I developed a program to recording (ALL-YOU-HEAR Input/Output) CrossFade these signals and send it to an endpoint over TCP-IP stack.
Options for Windows Win32 & Win64 : DirectSound, ASIO, WASAPI, WaveOUT, MIDI.
Options for Linux I386 & x86-64 and ARM : More or less the same.
You can use BASS for not comercial apps.