Although as a technique, bending is most often applied to single notes rather than chords, many intermediate students of the harmonica find that the 45i chord of the C harmonica is their easiest first bend to obtain. You should have already been applying the following effect to some of the blues verses previously presented, and to the train whistle. Placing your lips firmly on just those two holes, inhale with moderate volume while moving your tongue inside your mouth to say a series of "yo" sounds without moving your lips. If you listen carefully, the sound of the chord should be different when your tongue is in the "y" position (closer to the roof of the mouth) than it is when your tongue is in the "o" position (more open) of the "yo". When you can hear the sound change, use a "yo" effect on the 45i as a train whistle.
When you can consistently change the sound of the 45i chord with a "yo" tonguing, apply a similar effect to the single notes 4i and 5i. This effect may also be applied to the 56i notes.
Note: Other than the above bends, the ability to obtain a clear single note is crucial to the practice of bending. If you cannot hit single notes at will, your time will probably be better spent in the pursuit of the single note than in attempting to bend.
Bending is largely a matter of isolating the correct tongue position needed to bend a note by listening while you make tiny adjustments to your tongue position while inhaling. If the position is anywhere near the correct one, you will hear the note change. Experiment with pulling your tongue back into your mouth as you inhale, while raising the back of your tongue towards the roof of your mouth. When doing so, you may feel upwards pressure as the edges of your tongue press against your upper back teeth.
If you locate the correct position, the tone of the note will go lower and stay lower. If the note goes lower, then immediately pops back up, your tongue has travelled through the correct position and then gone too far back into your mouth, or too far up towards the roof of your mouth. It is difficult to maintain the proper tongue position for a bend, even though you may be able to hit the bend sporadically. Increasing the volume of the inhale when you think that your tongue may be in a correct bending position may help to encourage the bend to come through. Work with the inhale notes 6i, 4i, 5i, and 1i, as demonstrated on the recording, since they are the easiest to bend. The correct tongue position will be further back in the mouth the lower the note, thus for the 1i bend the tongue may feel uncomfortably far back in the throat, while for the 6i bend the move backwards and upwards from a normal position may be only a fraction of an inch.
As previously mentioned, the additional bending information in Progressive Blues Harmonica Licks Volume Two may help you develop your ability to obtain bent notes.
Some players find that the image of singing a normal note, then their lowest possible note, helps. If you can whistle, the action of whistling a note, then lowering that note by pulling the tongue back, is very similar to the motion involved in bending. Try whistling a relatively high note as you inhale, then lowering that note. If you can do that, you can probably apply that same tongue motion to the middle in notes such as 4i or 6i, and begin to produce a bend.
Some intermediate harmonica players find that they can lower the sound of a note by tilting the front end of the harmonica either down or up while playing a clear, single inhaled note from the mid-range of the harmonica. This shortcut mimics the sound of a bend by constricting the air flow as the flesh of the lip blocks part of the hole, although it provides little useful information about how to use the tongue and throat musculature to achieve the bend. Unfortunately, this "tilting" method cannot really be used to provide bent notes while playing.