As more and more apps arriving with Audiobus and Virtual Midi support I listed here best apps that allows you to control other apps with Virtual MIDI. There are different types of such apps: MIDI controllers, arpeggiators, sequencer etc. So I choose most essential apps for each category.
With these apps you can control other iOS music apps: synths, samplers, drum machines (like Animoog, Magellan, Sunrizer, SampleTank, DM1, DrumJam and others) or PC/Mac Desktop DAWs (Ableton Live, Logic, Cubase, Studio One, Reason).
The most important midi app: Midi Bridge
Midi Bridge allows to link different apps (that support midi) with each other providing great routing and filtering features (see more details and screenshots here).
Best MIDI sequencer: Genome MIDI sequencer
With Genome you can create unlimited number of patterns on 16 midi tracks. Each track can be routed to send signals via different MIDI channels (combine this with MIDI bridge and you get unlimited routing capabilities with different external devices and internal apps).
There are two views of the app: song view (where you can create and run new patterns, play patterns from different tracks) and pattern view where you can draw notes and automation curves (for velocity, modwheel, program change and even for custom cc's). By the way song view supports midi learn so you can launch patterns from other apps or from external midi controllers.
Most beautiful MIDI controller: MIDI Studio
MIDI studio comes with really nice looking MIDI surfaces. One of the great features are drum pads with velocity controlled by accelerometer. Customizable knobs and faders (you can customize midi messages data like channel, CC, value) allows you to change existing templates.
And wiith pro-upgrade option you can create your own surfaces from the big library of different elements. All the elements: x/y pads, knobs, buttons, faders look like real hardware controllers.
And if you are looking for Mackie-control surface you can buy via in-app store great template for Mackie.
Most creative MIDI app: Arpeggionome pro
With Arpeggionome pro you can create arpeggios with just finger touch. XY pads provides you control of note value and note length (all customizable) and with accelerometer you can control velocity. Highly tweakable parameters allow you to design arpeggios of different kinds from simple one-two notes to the complex ones (use key, scale, number of notes, step distance, note style, octave range and style and others to construct nice sounding and sometimes unexpected arpeggios).
Best MIDI arpeggiator: StepPolyArp
With StepPolyArp you can make arpeggios of any kind. You can customize any note and run arpeggio by playing note or chord in the real time (it can also receive midi notes via external devices).