I can get sharp and rapid changes in my whistle by changing the way air flows across the lateral part of my tongue. In my normal whistling posture, that part of my tongue does something like what it does during a particularly hard /ɹ/ sound: it basically presses into the top molars. During fast whistling (and arpeggios), one side moves to let air pass more like what that part does during an /l/ sound. The rest of the tongue seems to move a tiny bit forward and up to accomplish this change.
The end result is a very fast “flipping” feeling between notes and a bit of adjustment needed to hit the pitch I’m going for. By going back and forth between the two tongue positions rapidly I can something like double my whistling speed compared to glottal air control, though at absolute top speed there is a reduction of pitch accuracy and I find it hard to keep a bit of an excessively airy tone out of the whistle. The point, though, is that what used to be top speed is very comfortable while “double-tonguing”. (I don’t know if there’s a common term for this move. I just kind of figured it out back in high school after I heard somebody else do it and they couldn’t explain it beyond “I don’t know. I just do it.”)
I hope this is an accurate and detailed enough description to get the idea from. I’m a bit unused to discussing tiny movements of mouth parts, I’m afraid. Best of luck learning!
I can get sharp and rapid changes in my whistle by changing the way air flows across the lateral part of my tongue. In my normal whistling posture, that part of my tongue does something like what it does during a particularly hard /ɹ/ sound: it basically presses into the top molars. During fast whistling (and arpeggios), one side moves to let air pass more like what that part does during an /l/ sound. The rest of the tongue seems to move a tiny bit forward and up to accomplish this change. The end result is a very fast “flipping” feeling between notes and a bit of adjustment needed to hit the pitch I’m going for. By going back and forth between the two tongue positions rapidly I can something like double my whistling speed compared to glottal air control, though at absolute top speed there is a reduction of pitch accuracy and I find it hard to keep a bit of an excessively airy tone out of the whistle. The point, though, is that what used to be top speed is very comfortable while “double-tonguing”. (I don’t know if there’s a common term for this move. I just kind of figured it out back in high school after I heard somebody else do it and they couldn’t explain it beyond “I don’t know. I just do it.”)
I hope this is an accurate and detailed enough description to get the idea from. I’m a bit unused to discussing tiny movements of mouth parts, I’m afraid. Best of luck learning!