This Bottle Hang Drum is a beautiful sounding little instrument made of recycled and upcycled materials. It produces a wonderfully pure resonance that is akin to the sound of the hangdrum/handpan, but is played more similarly to a santoor or hammer dulcimer.

The instrument idea is not my own, but this design and rendition of it is - however, it's such an easy and flexible build that I'd encourage you to play with the design to find what works best for you! The instrument is cheap, if not free, requires minimal effort, is easily retunable and customisable, and has a ridiculously zen payoff in the music you can make with it - I can't give more encouragement for you to give this one a real go!

If you are more video inclined, feel free to watch the video tutorial I made on this instrument last year. The music throughout is primarily played on the instrument, but watch the last 10 seconds or so to see it in action.

(and if you like what you see (and hear!) here, please consider sending a VOTE my way for the Instruments Contest!)

Step 1: Materials and Supplies

As mentioned, this project is very customisable - there are only a few core materials, and the rest are customisable. See the notes below for more detail.

CORE MATERIALS/SUPPLIES

- 500mL Coke Bottle/s*

- Old bicycle inner tube valve**

- Scissors

- Bicycle pump

FLEXIBLE MATERIALS/SUPPLIES

- Wooden plank (for mounting)

- Percussion stand/tripod (for mounting)

- Drill + 30mm hole bit (for mounting)

- Elastoplast/tape (for mounting)

- Pencils (as beaters)

- Wool (for beaters)

There are a range of ways to mount the bottles, and mine is quite heavy duty but takes some drill work - no problems if you have a workshop, but maybe tricky otherwise. Alternate mounting systems include using rubber bands to sandwich them between two pieces of metal rod (see Kaboom videos in last step), cutting holes in a cardboard box, or just holding them in your hands and playing them like Boomwhackers.

The bottles are normally played with beaters. I used pencils wrapped with wool for some weight and softness to elicit as warm a tone as possible, but I've also played them with disposable chopsticks and they still sound great.

*I tested many varieties of soft-drink bottle, and found that the 500mL coke bottle is most resonant. The 1L bottle also works - it gets some lower notes, but is a little less resonant. I suspect that coke bottles are made to withstand some of the highest pressures, and so the stronger plastic has more regular vibrations and resonance patterns. However, as you'll see, it is easy to test any other bottles you happen to have once you've made the cap device, so try anything you get your hands on, and leave a comment if you find something else that works!

**I understand if you don't happen to have a bunch of old bike inner tubes handy. Neither did I. I found that bike repair shops had some, but in the end I purchased valves from eBay (non-affiliate link here). I imagine in the future that link will be broken, so look up "TR414 Tire Valve", and I hope you get some good results. Pay attention to the dimensions - I almost bought some that were designed for trucks, and were huge!

Step 2: Modifying the Bottlecaps

This project actually does nothing to the bottles - rather, the detail is in the cap. We are essentially installing a valve in the cap to allow the bottle to be pressurised.

1. Remove the cap of the empty coke bottle.

2. Use scissors to gouge a small hole in the centre, slightly smaller than the diameter of the valve you are using.

3. Push the valve into the cap, so that the valve's screw-cap protrudes from the top of the cap. The edge of the holes in the cap should hug the rubber valve tightly, so that an airtight seal is formed.

I never had issues with air leakage except on one poorly gouged hole. I found this method generally held the air quite well, only suffering noticeable leakage after a number of weeks.

Step 3: Making the Beaters

I made my beaters with pencils and wool. I found the weight of the pencil produced a fuller tone, and the wool wrap reduced the 'click' of the contact sound. However, some people use chopsticks too. Disposable chopsticks are light, cheap, and easy to come by. Reusable chopsticks tend to be a bit heavier and hence, and yet somehow not much fuller. Experiment with any rod-like object!

1. Tie a double knot around the pencil about 3cm from the end.

2. Keep tying single knots, stacking them up towards the tip. Finish with a double knot.

3. Cut off the excess wool.

As you can see in the image, my knots were beginning to come out (as I used a synthetic, slippery yarn) - so I would recommend applying a strip of double-sided tape, or glue, to the end of the pencil before knotting up.

Step 4: Tuning the Bottles

Now we can start making some tones! Screw the modified caps back on to the bottles, and connect them to the bike pump. As you pressurise the bottle, strike the concave section at the bottom of the bottle (where 'Coca Cola' is embossed) with the beater to hear the tone (and isn't it wonderful?). The higher the pressure, the higher the pitch.

I've never exploded a bottle before BUT please be careful. Given how strong the plastic is, if it goes, I imagine it will do so violently. Pressurise at your own risk. As a guide, I've safely reached C6 (1046Hz) before, but yours may go higher or lower.

Step 5: Making the Mount

This is the most flexible part of the whole build, and can be as simple or as elaborate as you'd like. I will just outline how I made mine, but I encourage you to find your own solution - mine's not perfect either!

1. Drill 30mm holes on a slight angle in the plank of wood. The angle will help keep the bottles tilted upwards for easier playing.

2. Test the bottles for fit. I needed to wrap the bottlecaps in a little bit of Elastoplast/cloth tape to thicken and pad them out a bit for a snug fit into the holes.

3. Drill a small hole in the edge of the wooden plank, and screw the plank into the percussion/tripod stand (I had an old, broken boom stand for a ride cymbal, with an exposed thread, so I used that).

If you choose to build this option, I would recommend using a thicker piece of wood. Mine was scrap from an attempt to make marimba bars long ago, so it's just what I had lying around.

Step 6: Play!

Insert the bottles into the holes (or whatever other mounting system you've created) and you're ready to play! There's no formal 'way' these should be played, to my knowledge, but one sensible way of arranging the bottles is to have the lowest pitch near you, and alternate sides (similar to a kalimba). This way, if you tune the bottles to a diatonic scale, you can make triadic chords using three consecutive bottles on one side. If none of that made any sense, don't worry - just experiment and have fun.

To begin, I recommend trying the following tunings:

A minor pentatonic: A - C - D - E - G - A - ... (repeat)

D natural minor: A - D - E - F - G - A - Bb - C - D

D harmonic minor: A - D - E - F - G - A - Bb - C# - D

D dorian (a personal favourite): A - D - E - F - G - A - B - C - D

...or if you're a contemporary art music freak (like me), go wild with microtonal tuning.

Beyond just striking the bottles, there are some other techniques you can try:

- Buzz: if you gently press the beater into the bottle as you play, you get a tight buzz (works best with chopstick beaters) which can be a lovely accented effect.

- Percussive sound: strike on the convex neck or base of the bottle for a pitchless click, which can add to your groove.

- Chords: if you strike a far bottle with a relaxed grip, and swiftly move your hand towards yourself, the beater should rebound off the bottle, and strike others as it moves towards you. In this way you can play entire chords with one stroke.

I'll leave you with a couple of videos by Kaboom Percussion, an Australian percussion duo and good friends who adapted this project for use in their shows and videos. They really took this project to another, truly inspirational level. If you haven't seen them before, certainly check out their work and give them some likes and subs! (The observant among you may notice in my video, there's one unfilled hole - that bottle was with Josh from Kaboom to model while they built theirs!)