Before you hear the Met's 'Hansel and Gretel' broadcast . . .

Engelbert Humperdinck's ''Hansel and Gretel'' -- to be broadcast live from the Met Saturday, Jan. 9, at 2 p.m. Eastern standard time (check local listings) -- has been a family favorite for most of its existence. Its blend of youthful naivete and Wagnerian inspiration have kept young and old enthralled.

Until recently, there were numerous performances on LPs from which to choose, including an RCA set (ARL2 - 0637) -- currently deleted though still locatable in many stores -- with Anna Moffo and Helen Donath as the two children, and Christa Ludwig as the Witch.

However, when Columbia Masterworks released its set (M2 - 35898), all stereo competition was swept aside. Ileana Cotrubas is a delectable Gretel, Frederica von Stade a fine Hansel, and Elisabeth Soderstrom sings the Witch and still manages to make it a galvanizing performance. Miss Ludwig is the Mother here, with Siegmund Nimsgern as the Father, Kiri Te Kanawa as the Sandman, and Ruth Welting as the Dew Fairy (lavish casting in the latter two!). John Pritchard is the loving solid conductor

Sir Georg Solti's account of the opera (London - 12112) is the conductor's show all the way. Not that Brigitte Fassbander and Lucia Popp aren't fine as the two children, nor that Walter Berry and Julia Hamari aren't up to the parents' music, nor even that Norma Burrowes and Edita Gruberova aren't lavishly cast in small roles. It's just that Solti and the Vienna Philharmonic make extravagent music together, which even the shrill cackling Witch of Anny Schlemm can't mar.

Another conductor's set is widely available on British import (EMI SLS - 5145 ), with the Philharmonia Orchestra led by Herbert von Karajan. In truth, this is the most beautiful set of the work available, but it is in electronic stereo (well done, but not as technically plush as the Columbia set). Elisabeth Schwarzkopf and Elisabeth Grummer are the siblings, the rest of the cast is good indeed, and Karajan gives the score all the breathing room it needs.

All the above sets are in German. A sung-in-English set is around on Columbia Odyssey (Y2 - 32546) recorded with the Metropolitan Opera forces in 1947. Rise Stevens and Nadine Conner are the children, Thelma Votipka the Witch , John Brownlee and Claramae Turner the parents, and Max Rudolf conducts. It's a good set and a fine document of high standards back then, even in so ''routine'' an assignment as this.