This warmup was designed by legendary clarinetist, Louis DeSantis (1893-1940), and is excerpted from his book, New Studies for the Clarinet. (https://azmusicmasters.com/products/new-studies-for-clarinet-by-louis-desantis) The book was originally published in 1920 and has been beautifully reconstructed by clarinetist Russell Harlowe. It is a wonderful compilation of etudes based on famous clarinet cadenzas from the orchestral repertoire in addition to original exercises created by Mr. DeSantis. None other than Robert Marcellus often stated that Mr. DeSantis had the most beautiful clarinet sound.
The arpeggio exercise below moves through all the major and minor keys and is to be played early in one’s practice routine. I have copied it as it appears in the book with a slight phrasing variation at the end of each tonality. It can be played with varying combinations of articulations and dynamics, while the sequence allows for extensions into the upper and lower registers as well. The focus should be on a smooth finger technique employing minimal key pressure AND legato connections throughout the registers so that all notes have the same quality of resonance.