Expose a audio stream or allow to provide a path where to store the mixed output

[kuamanet]

engine.mainMixerNode.installTap(onBus: 0, bufferSize: 4096, format: nil) {(buffer, time) in
            do {
                try outputFile.write(from: buffer);
            } catch {
                // We cannot re-throw here due to the signature of the block
                print("Error: \(error)")
                print("Description: \(error.localizedDescription)")
            }
        }