With the cassette format well established among hi-fi enthusiasts we can expect continuing improvements in machinery and cassette tapes. Cassettes need no longer "prove" themselves as a serious sound format; they have entered a phase of development characterized by small but significant refinements.

For instance, new Sansui cassette recorders feature "direct-o-matic" front loading that facilitates inserting and removing a cassette. During tape movement, small arms extend from the sides to hold the cassette in place.

Tape movement may be controlled by "fast-buttoning," and an elaborate memory/autoplay/auto-repeat system can be engaged to get the tape to "do tricks" such as automatically rewinding and/or resuming play, and so on. A special button advances the tape briefly at fast-wind to get past the leader section. These are real improvements and not mere gimmicks, and it is to Sansui's credit that these features have been combined in a machine (judging from the model SC-5100) that also has the primary attribute of excellent sound.

The "super ANRS" feature of the recent JVC "KD" series has been mentioned in an earlier column (it permits higher-level recording of high-amplitude, high-frequency signals). In addition JVC's new models have an extra recording-equalization control to further aid in precisely matching a given tape to the deck. On its top AD models, AIWA offers the option for fine-adjustment of recording bias to achieve the same purpose.

Among Teac's recent improvements are the use in its model A-640 of a phase-locked loop for improved transport characteristics, and in its lower-priced A-103 a new internal design that uses a single circuit board instead of complicated wiring. The A-103 also boasts a "cushioned" cassette-eject mechanism that pushes out the cassette slowly and gently.

Three-head cassette decks continue to grow in number, slowly of course, with the recent line from Fisher claiming to be the lowest-priced models to incorporate this feature. At a list price of about $350, for instance, the Fisher CR-5120 boats an enviable roster of features, including - in addition to three heads - a two-motor, dual capstan transport; Dolby-B; EQ and bias selection; etc. Just how good this machine is at that price remains to be determined; apparently it is still too new to have been released for evaluation. Tape companies are falling over each other to release their favorite cassette formulations.

For one, the 3M Company has three new recording cassette tapes in its Master series. Master I is for normal bias; it is a high-output ferric-oxide tape. Master II, a ferricobat formulation, takes the higher chrome bias (and the 70-microsecond equalization). Master III is the new "hybird" - ferrichrome - which also takes the higher bias but is said to enhance the high-end response regardless of bias and EQ.

In prerecorded cassettes, Advent continues to earn laurels for its stunning releases in the CR/70 series. The latest is Handel's Messiah (EE 1061), beautifully performed, brilliantly recorded and processed, and out in time for the holiday season.