| Jack,
I'm such an idiot that I started writing and forget the larger question you asked about!
DTing intervals comes as a result of doing the ground I discussed before but I neglected to remind you that DTing wide intervals requires the same open throat yawning style that a proper sounding octave slur does. One can slur octves with a great amount of intra-oral overmanipulation but the sound suffers as the lips and throat close between the notes. You want to practice the wide slurs and DT in tandem, back and forth and find their common point of sound. That will be your reference point always.
ML |