What causes the note duration of midi tracks to extend far beyond the actual note value when opened in BiaB? Is there some setting that I am missing?

HI
Do you mean as heard or as displayed in the notation screens.
The note length of a midi note is the difference between when you first press the key (note on) and when you release the key (Note off). This is what you will see in the notation and these times a written in the file as data on the timeline.
What you hear will depend to some extent how much reverb you have on it and also the instruments note decay time.

Also where as a Piano note will die eventually even with sustain pedal down no mater how long you press the key down, a continuous voice like a flute will sound until you release the key.
Mike

thanks Mike,
I actually did not play this tune into BiaB but rather took a midi file that I had and filled out the tracks in RB then opened it in BiaB. The tracks played very muddy sounding and when I looked at the notation for the melody it showed the note values as they were written but in the edit mode showed the note time line greatly expanded. I know how to adjust each note but this is a long song and I was wondering if there was a global reset to the written note values.

Probably not the same issue (but, hey there may be bleedover), I have found on occasion that MIDI note values for BIAB MIDI track arrangements get extended for no good reason. Then you end up with a drone sound as the wrong notes keep playing across your chord changes.

My suspicion (with no proof) is it has to do with the feature to make "strings" track data smooth (for example, on the strings track in BIAB, if you play a C chord (C-E-G) and then move to an Am chord (A-C-E), BIAB just keeps playing the common C and A and only changes the G to an A. This is great for lush string sounds, but...

Again, I'm just speculating, but not sure why it does it randomly and not on every track, and not sure if it's related to problem at hand.

I have also seen MIDI files (from my notation program) imported into BIAB do the same thing, even though they clearly have assigned note durations. Since it's sporadic, I just fix it in the piano roll window, where it's easy to see the overlapping notes.

HI again

Although you did not play the midi notes in someone did when the midi file was made or made it in step mode. Either way the note values would have been specific.

Legato type playing can cause problems in midi files as often used for string parts,
As John says there are auto legato settings to watch out for.
The problem can causes overlapping midi notes as it is achieved by hanging on to one key until you play the next note. If the notes are of a different pitch this should not be a problem apart from any polyphony problems, but if the notes are the same pitch it can result in the note off from the previous note not being acted on and then you will get the stuck note drone.
Mike

AFAIK there is no global reset. However you may be able to go to the piano roll view, select all, then shorten all of the notes simultaneously. I know this works in most DAWs but I do not know if this will work in BiaB.