Just downloaded Electron. [App store link] My first impression is that this may be a little more advanced than many of the other "Matrix" style music apps. Electron allows multiple layers and patterns as well as the ability to change pitch and instrument sounds. 

Upon opening this app you are greeted with a 16x9 LED matrix. After about 5 seconds the Song List view scrolls up from the bottom giving you the opportunity to either load a current song or create a new one. You get to name your song, tap the Create button and you're back to the matrix. At the bottom of the screen are several navigation buttons. Rewind, Play, Layer and Pattern selection, Options, and Mode.

Programming beats is fairly straight forward. If you've used a matrix style app or step sequencer/drum machine before it should be second nature. Press the play button and tap an LED once to activate it, a second time to deactivate. You can also tap/hold and any LED that falls under your touch will be activated, (if the first tap landed on a inactive LED) or deactivated depending on the state the initially tapped LED was in. This is great for making trills/drum rolls or for erasing big chunks in one go. 

There are 4 layers (1, 2, 3, 4) and 8 patterns (A - H). Each layer can hold any one of the 15 available sounds, so you can actually have 4 "voices" active at once. Pitched instruments rise in pitch from the bottom row to the top row. Drum kits work a little bit differently though, each row is a different drum sound, arranged in a fairly conventional way from the bottom row up: Kick, snares, percussion, claps, cymbals...

Sounds can be accessed with the Options button (Gears). This brings up the Options panel. There's actually a whole bunch of pretty useful stuff in here. You've got Exit Options, Move Up/Down/Left/Right, Cut/Copy/Paste, Delete, Undo, Menu Placement (top/bottom), Preferences, Instruments, Play Along and Tempo. Tap the keyboard icon to enter the Instrument screen. (Remember some of these screens are Layer specific so the instrument will be changed for whichever layer you had selected when you entered the Options panel.) Here you have the options Select Instrument and Instrument Tuning. Choose an instrument and tuning configuration and click Done. Select a different layer and repeat the process. You can also change instruments from the Preferences screen under Layer Information. You may find this a little quicker. Whichever way you choose there is one major drawback. Entering the Instrument screen stops playback. So you can't actually audition instruments without a lot of menu hopping.

Play Along Mode is interesting but may not be very useful. Tapping the Play Along Mode button allows you to "play" the LED's instead of activating/deactivating them. Try it and let me know.

The only other trick in this bag is Song Mode. You can access Song Mode with the grid button in the bottom right corner of the screen. The interface does a nice flip transition. To go back, tap the grid again. Once in Song Mode you'll see your four Layers listed down the left side and a 32 column grid stretching out to the right. (Only the first 10 columns are visible until you flick/scroll.)

Each square represents 1 measure. To create a song you simply fill the measures with patterns. You can do this by double tapping in the square and selecting the appropriate pattern from the pop-up window. The copy and paste functions at the bottom of the window are great time savers.

There are two hidden functions in song mode, muting and looping. You can mute any of the layers by tapping the colored orbs to the left of each layer number. Tap again to unmute. Looping could use some improvement but at least the function exists. Currently you can only define the end of the loop. Set the loop point by double tapping a measure number at the bottom of the screen. The song will play through this measure and loop back to the first measure.