Hexadecimal Drum Machine
Create your own rhythms!
And learn about binary, decimal and hexadecimal numbers, too.
Also try Hexadecimal Drum Machine HTML5 version
Instructions: Click on the lights next to each type of drum, or change the Rhythm Number. (Hint: if you like a rhythm, save the rhythm number  you can come back and reenter it later.) Also read the explanation below.
Explanation
There are 4 instruments (HiHat, Snare, Tom and Base). At any point in time any combination of them can be played.
If you write down "1" for Play and "0" for Don't Play, then you could have a combination like HiHat and Tom being "1010", or HiHat and Base being "1001". All four together is "1111".
This is called "Binary", because there are only two choices (Yes or No) for each digit. A single binary digit is called a "bit". The word binary comes from "Bi" meaning two. We see "bi" in words such as "bicycle" (two wheels) or "binocular" (two eyes). 
So, at any point in time these are the possible combinations (1=Play, 0=Don't Play):
HiHat

Snare

Tom

Base

Combination

As
Binary 
As
Decimal 
As Hexa
decimal 

0

0

0

0

0000

0

0

0

0

0

0

1

0001

1

1

1

0

0

1

0

0010

10

2

2

0

0

1

1

0011

11

3

3

0

1

0

0

0100

100

4

4

0

1

0

1

0101

101

5

5

0

1

1

0

0110

110

6

6

0

1

1

1

0111

111

7

7

1

0

0

0

1000

1000

8

8

1

0

0

1

1001

1001

9

9

1

0

1

0

1010

1010

10

A

1

0

1

1

1011

1011

11

B

1

1

0

0

1100

1100

12

C

1

1

0

1

1101

1101

13

D

1

1

1

0

1110

1110

14

E

1

1

1

1

1111

1111

15

F

In the column next to the Binary Numbers are the matching Decimal Numbers and then the Hexadecimal Numbers.
Hexadecimal Numbers
The Hexadecimal numbers are interesting. They look the same as the decimal numbers up to 9, but then there are the letters ("A',"B","C","D","E","F") in place of the decimal numbers 10 to 15.
So a single Hexadecimal digit can show 16 different values instead of the normal 10.
How does this help?
Well, in this case it means that a Rhythm Code can be written as "90D2C0819082C0A4", instead of "9,0,13,2,12,0,8,1,9,0,8,2,12,0,10,4".
It is a more natural way to show anything that has 16 combinations ... in other words it is "neat".
Computers
Also, computers love binary (and hexadecimal) because the computer circuits and memory are based on "on/off" (either a signal is there or not).
For example, the pictures and sound on a DVD are recorded as tiny little holes that can be "read" by a laser. As the DVD spins, the laser detects if there is a hole (or not) at every location. This is turned into a series of "1"s and "0"s that the computer then turns into sound and images. 