Building own instrumentsProper samba instruments aren’t cheap (although you can sometimes get good bulk deals on internet and from specialist suppliers) but not having instruments is no excuse!!! Some samba started off life as a junk band, and you can too. If you look back at the history of samba, improvised instruments feature strongly. When a military junta ran Brazil in the 1960s and 70s for example, street music or indeed anything considered "cultural" was viewed with suspicion and playing samba could get you arrested. So people used frying pans, table tops, match boxes, clapped hands - indeed anything that could be put to more innocent uses if the army showed up. To put it another way - go with what you’ve got.
So, making the instruments is the obvious first step. Look at the instruments section of this site to find out the type of instruments you’ll need. Some of them, such as the caixa may be hard to improvise, but the others should be achievable from junk. As a rule, use containers, plastic and metal, and experiment with different levels of pitch and bass.
CaixaSnares can be hard to improvise (but can be got cheaply second hand). In the long term you’re probably best off investing in proper ones early. Until you do, try getting a large metal can (e.g. a large coffee can) and putting some coins in it. How many depends on the size of the can. Glue a rubber mouse mat over the top. You might need to play with the number of coins you put in to get the right sound. The coins jingle and bounce, causing the "snare" sound. Plastic 1-gallon buckets also work OK.
ShakersThe Shaker section can make their instruments from two food cans with the tops cut off, filled with small hard objects (ie dried beans, lentils, rice etc...) and taped together (and painted pink, of course!). Making as many of these is a good idea as you can hand them out to others when you play. You can also make good shakers by nailing bottle tops, little foil fruit pie tins, buttons, tin cans, spoons, the metal parts of 3.5" floppy disks etc loosely to a stick. If you thread them horizontally, you get a very good approximation of a Chocalho. Be careful though – sticks with nails can be mistaken as offensive weapons by stupid people. Tape over or file down any pointy bits.
Build your ownwooden Chocalho, see here
SurdosSurdos can be made from large plastic or metal containers - think bins, water butts, large storage drums etc. Metal or plastic bins with drum skins attached work well It will be important to get the three distinct surdo levels (ie. low, middle and high) so try and find containers of different sizes. Surdos comprise the back line of the band, keeping time and providing a cracking bass beat. It’s worth taking time to get this right early. Some bands make bass drums out of those giant cardboard tubes from the middle of carpet rolls (just ask at your local carpet store) with lots of layers of cling film stretched over them and gaffer taped down to make skins. They’re not the most resilient in the world (you really need to play them using plastic bottles as sticks), but they sound brilliant, they’re eco friendly and could serve if you’re starting out and have no cash at all!!!
RepeniqueThe repenique can, again, be made from some container or other (buckets or large water cooler bottles). Keep in mind that it has a very loud sound due to its very taut skin. Try to replicate this.
TambourimsTambourines are served very well by pots and pans. Try to find something that gives a nice high pitched "crack" when hit.
To change tamborim skin, see here
SticksWooden spoons make good sticks, esspecially for the repenique
Surdo BeaterThere are good instructions for making surdo beaters on the web. One technique using batting and latex ballons is described here and here
Here, you find another instruction tested and approved by RoR bands
Re-use drum kitAlternatively, cannibalise an old drum kit! Bass/ kick drums work as impromptu surdos, whilst smaller toms can sub for repeniques. Just strap ’em on and off you go. Be careful though - the nuts and rods on drum kit drums are not designed to hold the weight of the drum. Before you start, pass a strap or some webbing all the way round the drum under all the rods. Use that to attach your carry belt/ strap to.
Whatever you do, try and avoid things that someone might mistake for a weapon. Think cheap, durable, loud and not aggressive looking. If it has any pointy bits, file them down or tape them over. Better safe than sorry!
A Good article about drumming where you can find DIY and other tips on it here