YouTube via icegearnet. This will run on the iPad as well. "ARGON, virtual monophonic synthesizer for iPhone. For more information, visit our site. http://iphone.icegear.net/a..." on iTunes:
Update:
"Updated version(1.1.0) of the ARGON (iPhone 2G/3G/3GS and iPod touch; $1.99) is now available at Appstore [link above].
ARGON helps you to create new sounds by using the included three Oscillators, a filter, an amplifier, a saturator and a delay. Also 64 factory presets and 512 user presets are included.
The Oscillators have various waveforms and FM and AM, oscillator sync and oscillator modulation.
Filters have four lowpass (24dB, 18dB, 12dB, 6dB), band-pass filter, highpass filter, and envelope/LFO.
The Amp offers overdrive (saturator), 3-band EQ, panpot and envelope.
The Delay Effect offers L/R delay. It also includes Tempo Sync, an LFO and a spread parameter.
In particular, you can make your own pattern with Step-Sequencer. And you can also make sound like human voice with Formant Oscillator.
Loop Recorder is newly added feature to 1.1.0 update. You're able to overdub on the recorded loop while playing it and export the piece you made to your computer as .wav file.
YouTube via zibbybone "Here are the ROM play demo songs for the R8-M and 6 of the PCM sound cards. All songs Copyright Roland Corporation. The PCM cards featured in this video are: SN-R8-02 Jazz Brush SN-R8-03 Sound Effects SN-R8-04 Electronic (TR-808) SN-R8-06 Ethnic Percussion SN-R8-09 Power Drums U.S.A. SN-R8-10 Dance (CR-78, TB-303 & TR-909)"
YouTube via djgalactic "This a new home made pattern with the Electribe Korg EMX-1 Groove Box Da Zound Electronic Music (Techno / House) By DJ Galactic"
YouTube via jetdaisuke "http://webdog.be/archives/10205_02131... ピアノロールシーケンサーを打ち込んでループを配置していくだけで曲ができるiPho neアプリ。かなり不思議な作曲体験を味わえます" See this video for a tutorial. Remember, all iPhone apps will work on the iPad out of the box.