Electrum Drum Machine/Sampler
When I tell people that I've been doing drum-machine programming on my cell phone, I typically get one of two reactions: Either they laugh at the notion and assume that this is some sort of gimmicky app, or else they think it's the greatest thing ever. So far I've probably encountered more of the first group. However, when I show them how Electrum Drum Machine works, they often fall into the latter camp. The app is actually a powerful tool, and anyone who has used a professional-quality drum machine should be instantly familiar with how to use it.
Electrum Drum Machine uses a typical and intuitive pattern arrangement for selecting drum beats. It also has a variety of drum-machine sounds that you can load, including the extremely popular Roland TR-808 and TR-909 sounds that show up in all your favorite techno, electro, and rap songs. Programming individual beats is incredibly easy. Sequencing all those beats together is a little less intuitive, but the help menu provides easy-to-follow instructions.
What makes this app genuinely useful is that you can export the patterns you have designed as .wav or MIDI files, so the program is essentially compatible with a wide assortment of music-making programs. The sound quality of the audio files is clear and good. It may not meet the highest audio standards, such as what you hear coming out of professional studios, but that's becoming less important in a world where everyone listens to MP3s on iPods.
I have only two minor issues with Electrum Drum Machine. First, I wish it offered a way to e-mail audio files or otherwise transfer them from the app without my having to connect the Android device to a computer via a USB cable. Second, the help screen has a sluggish response to user input. (Luckily, the instructions for the app are also available on the app maker's Website.) Despite those minor criticisms, I recommend this app as a powerful tool for making music.