Can you whistle with a blade of grass? We used to do this all the time as kids when we were out for walks.
For me who can't whistle, at least this is one way I can make a kind of whistling noise!
When our eldest daughter was practising her clarinet yesterday - I took our younger daughter outside to show her a reed instrument she could play outside to make a similar noise to her sister's clarinet!
You find a blade of grass that is nice and wide, and place flat and taut it between your thumbs as shown in the picture above. Then you blow through the small gap just below your thumb knuckles - through the edge of the blade of grass. This makes a kind of whistling noise.
It took a little playing around with, but we managed it in the end and had fun playing our own reed instruments!
My daughter then told me that a friend at school had whistled using a leaf in a slightly different way. I'd never heard of this before - but good old You tube had a couple of videos - and after watching this one, I found a leaf in the garden and managed to make tuneful sounds with that too!
And here's the link to a 2 minute video of a man playing an amazing version of Eidelweiss - with a leaf!!!
So - why not go out into your garden and find your own musical instruments for yourself and your kids and start practising!