The All Is Yar blog, an indispensable source of intel about the Los Angeles Philharmonic and other Southland musical goings-on, has several updates on personnel changes at the orchestra. First, several violinists are trying out for the concertmaster chair, which Martin Chalifour vacated over the summer. Yoonshin Song, from the Houston Symphony, is guest concertmaster for the first three weeks of the season. (Nathan Cole, formerly the associate concertmaster, would have been a plausible successor, but he has decamped to the Boston Symphony.) Second, as has been known for several months, Ryan Roberts, the English-horn player of the N.Y. Phil, has assumed the principal oboe position, which has been a revolving door in recent years. This afternoon, I heard Roberts in the Alpine Symphony — a perfectly judged rendition of the halting “At the Summit” solo, crisp in timbre yet fluid in expression. Roberts is a native Angeleno and must be one of very few active surfers to have occupied oboe chairs in leading orchestras. Finally, All Is Yar relays the excellent news that Wesley Sumpter, who was a Resident Fellow with the Phil from 2018 to 2022 and has been freelancing in the percussion section since then, has been offered the Assistant Principal Percussion post. I recall Sumpter guiding audience members through a rendition of Pauline Oliveros’s Rock Piece at the 2018 Fluxus Festival. With a patient smile, he made everyone start over because, he said, some of us couldn’t have found an independent pulse in the environment so quickly. He combines technical finesse with breadth of vision — an ideal orchestral musician.