The first one is: doing a 'mmm' sound as if to say 'poor me'. The sensation of where the sound comes from is in the head/behind the nose. Start at a high note and gradually go down to your lowest note in one long 'poor me' curve. You can do the same with 'aar', 'ee', 'ay', 'or' and 'oo'.

The second one is: when exhaling, be noiseless and come on to the (ar) sound gradually. Keep smiling when you are doing this. You may feel silly at first but I assure you, you will get used to not being conscious of that after a while. Back to the exercise, keep smiling when saying 'ar'. This feeling is like yawning. You feel relaxed. You can do some more with different sounds: 'ee', 'oo', 'or' and 'ay'.

MORE EXERCISES TO RELEASE TENSION
Tongue
1. Massage the base of your tongue.
2. 'Tongue root jiggle'. Vibrate the base of your tongue under the chin with 2 fingers or 'er' sound. Then do them without the fingers.
3. Stick your tongue out like a lion to release tension at the back.
4. Curl the tongue backwards.
5. Roll the tongue as in a 'tril'. Now I know, not all of you will be able to do this but don't worry if you can't.