Play long-note slurs in and out of those regions. i.e. low C up to G -hold the G- back to C, and the reverse: high C down to G -hold it- and back up. Use intervals in the overtone series, i.e. the same fingering for each set of notes.
Also get a standard flexibility exercise book like Chas. Colin and play these slowly, using them more as long-tone exercises.
High C as a beginner with no problems and clear as a bell? I hate you!
Also get a standard flexibility exercise book like Chas. Colin and play these slowly, using them more as long-tone exercises.
High C as a beginner with no problems and clear as a bell? I hate you!