I copied and pasted this from my "Keep Up With Your Apps, Fool" list I have. There were also some less than desirable music apps on there as well as some non musical apps. I deleting them for this post but must have deleted some keepers accidentally.

Chordbot is definitely one of those especially now with the great update as Kevin mentioned.

Also missing from the list is the must have AudioBus. For the first time on iOS you can record audio through the bus to another recording app. Prior to AudioBus, one had to audio copy and then audio paste to another app that supports audio copy/paste. Sometimes, this had to be done via email, dropbox, fps, etc. AudioBus is still in its infancy so there are only around 20 or so apps that support it thus far but will certainly grow as the sdk is made available to more developers.

Auria and BeatMaker 2 are my most used DAWs. Auria has not yet implemented MIDI so BM2 gets the nod for sequencing MIDI. Neither support AudioBus yet but the developers are working on it. Multitrack DAW supports AudioBus so I use it frequently to record audio from other apps then paste it into Auria or BM2.

JamUp Pro takes good care of my guitar needs and supports AudioBus. I bought the JamUp Plug guitar audio interface but it is a little finicky with feedback as it is going through the iDevice mic input. I now use a Griffin StudioConnect Audio/MIDI interface for guitar, acoustic and vocal recordings. This works much better. And it props up the iPad on my desk for convenience.

I like DrumJam and DM-1 Drum Machine for my percussion needs. DrumJam supports AudioBus and DM-1 will be on the bus soon. Sorely missing from iOS is JamStix. The developer has future plans for us though.

SampleTank and GarageBand are the apps I use most for piano sounds. Both have decent strings and other bread and butter sounds. The Smart Instruments in GarageBand make it easy to scratch out ideas quickly.

There are some really great synth apps available that make it hard to choose a must have. Currently the most used would probably be Magellan, Animoog, Alchemy, Addictive, and PPG Wavegenerator. It all depends on what sound I am trying to achieve. Audulus looks like a great modular synth maker but it requires iOS 6 and I'm not ready to upgrade my iPad yet. I upgraded my iPod to iOS 6 and it stinks.

I'm not much of a keyboard player so I really enjoy using some the interesting alternative GUI MIDI controller apps. Orphion, Geo Synthesizer, Cantor, Chordion, and Musix Pro provide very unique and helpful ways of sending out MIDI to other apps for non traditional keyboard layout players. I also design my own interfaces on Beatsurfing and TouchOSC though TouchOSC requires a PC for customizing layouts.

Hopefully that narrows it down a bit for possible must have apps.

Good luck on what you chose to get.

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