Innov8tv - You touched on the reason for the double notes. Those are there to accomodate instruments that may not have the range of the outside notes. Since this is a "unison" type exercise, vibes will have limited range as compared to marimbas, so if the outside notes aren't available, these instances offer a substitution that can be made. No need to play the upper note with RH. Even at moderate speeds, that wouldn't be very feasible.
Hope this helps, and that you're enjoying the book!
Legacy Forum Post
In measure 3 of "Yak-scents" on page 126 of Up Front, the ah of beat 3 and the e of beat four have two notes written. This does not occur elsewhere in the excercise. Is this a typo or were there two notes written for the sake of varying instrument ranges? Or, should the right hand move to play the upper note?
Thanks for the help in advance....