When I start a song, any song, but I discovered this with one I created as the patch seems to be louder, I can hear the song starting just as the 4 intro beats start at the same time.

I muted all instruments and I made sure there is nothing in the audio track, but when I start the song, as the drumsticks are sounding the lead on beats, I hear the chords playing very, very softly in the background. The volume is so low that the moment the actual song starts, it disappear even if I am playing a soft ballad or a single channel is playing, but if I mute the instrument(s), it is quite audible. It barely has enough volume to push the VU meter above the background hiss (if I have anything plugged in) but one can tell something is there.

I just checked, and the song is playing through the "Through" channel, even though that is muted as well.

This is what I did just as I was writing this post (It made me think, so you guys helped before I even posted this):

1) I went to check on the VU Meters (or levels) to see if the sound was higher than the background hiss of my guitar amp.
2) I turned off my amp (by muting it at my sound card) to compare. Indeed, the unwanted sound from BIAB it is just slightly louder than the hiss of my amp coming off my phone (I use Jamup Pro and like it better than anything my PC has, weirdly enough)
3) I clicked on the "Through" button and that channel became visible. It was muted, yet the sound of the chords persisted (Tubas? French Horns? I can't tell)
4) I unmuted the master mute, and that made no difference. Chords keep playing.
5) I unmuted the "Through" Channel and that made no difference
6) When I muted the "Through" Channel again, BINGO! The sound of the chords stopped! Only to start again after a few moments. About the same delay I describe below and the same delay it has when the song's countdown starts at the beginning.
I was able to repeat this reliably. Additionally, I noticed that the patch "Tubas" was selected in the "Through" channel. I changed the patch first to another instrument then to nothing, but it made no difference.

I unmuted the whole song, almost blasting my ears off because to hear the stray chords I have to have the volume high), then I clicked on the global mute and all sound stopped. Only for the chords on "Through" to start again after a bar or two.

For the record, the sound responds to the "Through" channel volume and pan, beside responding to mute. There is no doubt where it's coming from.

Right now it's set to instrument: -0 <No patch change> but the Tubas are still playing as if I didn't touch it.

Another couple of curious facts:
1) the stray Tubas are a full bar ahead of the song as they start the instant I hit play but ignore the lead on count, so the chord changes play as the drummer hits the sticks.
2) They are actually a bar ahead, but 1/8 behind the song, not a precise bar. At least, visually speaking, it looks that way as the chord changes 1/8 after the bar blackens, and at the start I can hear the first lead up click, then the chords, then the second click, so it is starting someplace in between the first two beats.
3) The sound is MIDI generated. I inserted a chord in between the song's first two chords and dutifully it played it. So it's not some sort of looped recorded sound coming from someplace else. It is part of the MIDI data.

Well, sorry for the rambling post. I was active in this community back on 2009 but I have since lost my account and related email. I am starting again with my old BIAB 2008 but it has been a long time. It could be I am messing up someplace, in that case my apologies, but this seems very strange to me.