|Clip art: Clker|
In pre-focal there is a natural build up in pitch and volume that is less evident after the focused syllable. The idea is to concentrate on compression, not softening or simply lowering volume, from the learner's perspective--as most methods recommend. Conceptually, the space between the syllables is what is being compressed; in reality, everything is, of course. (Check this note from University College London Phonetic Lab.)
Of all the protocols, this one often has the most dramatic and immediate effect. (What you see in the video is the final "product," not the pedagogical sequence that leads up to it, but you can probably figure out a version of that yourself.) So . . ."take the gloves off" sometime and go a few rounds with your class, especially if they are predominantly native speakers of "syllable-timed" L1s. It is great for "de-compressing" as well!