The popularity of the cello has increased significantly over the past few years, with the classical instrument now found in rock bands, jazz ensembles, and traditional Scottish music. Back on the classical side, the cello is given its due this week at the ninth annual Jezreel Valley International Cello Seminar (December 17-22). An impressive host of cellists on its faculty - Emanuel Gruber, Michael Haran, Enrique Maltz, Zvi Plesser, Hillel Zori and other internationally known artists - will be on hand for the master classes and concerts, all held at the Jezreel Valley Center for Arts and Culture. Distinguished cellist Gary Hoffman, a seminar faculty member, also takes the opportunity to lead master classes at the Jerusalem Music Center in Mishkenot Sha'ananim, to which the general public is invited (Sunday, 10:00-12:30 and 2:00-5:30). On Monday he will give a recital there of works for solo cello by Bach, Reger and Gaspar Cassado (8:30 p.m.) Cassado was a great cellist and student of Pablo Casals, and this virtuosic piece is Catalan in flavor. Paris-based Hoffman plays all-gut strings, explaining that although they demand a more precise bow technique than steel ones, they compensate by yielding more color and variety. On Tuesday he will be teaching at the Jezreel seminar. For further information about Gary Hoffman's master classes and recital, call (02) 623-4347. For further information about the Jezreel Valley Annual International Cello Seminar, call (09) 749-3233.