Hello valfis86,
you can use BassMIX too for changing the Volume. I made a quick Console Application Demo in C# to show you how it is done. It starts with the normal Volume and after the Users presses a Key it goes down to 40% Volume.
static void Main(string[] args)
{
//Init
Bass.BASS_Init(-1, 44100, BASSInit.BASS_DEVICE_DEFAULT, IntPtr.Zero);
//Create Mixer
int mixer = BassMix.BASS_Mixer_StreamCreate(44100, 2, BASSFlag.BASS_DEFAULT);
//Create Source Channel
int play_stream = Bass.BASS_StreamCreateFile("test1.mp3", 0, 0, BASSFlag.BASS_STREAM_DECODE);
//Add Source Channel to Mixer
BassMix.BASS_Mixer_StreamAddChannel(mixer, play_stream, BASSFlag.BASS_DEFAULT);
Console.WriteLine("Press Key to start Playback");
Console.ReadKey();
//Start Playback
Bass.BASS_ChannelPlay(mixer, false);
//Wait for Userinput
Console.WriteLine("Press Key to apply Envelope (Volume 40%)");
Console.ReadKey();
//Create nodes for Envelope and apply them
BASS_MIXER_NODE[] nodes = new BASS_MIXER_NODE[1];
nodes[0].pos = 0;
nodes[0].val = 0.4f;
BassMix.BASS_Mixer_ChannelSetEnvelope(play_stream, BASSMIXEnvelope.BASS_MIXER_ENV_VOL, nodes, 1);
//Keep Console Window open
Console.ReadKey();
}
