Maria Calfa-DePaul has been responding to comments in the original post about powering a USB keyboard with the Duracell Powerhouse.

The main question on everyone's mind has been, "How long will this thing actually last?" The answer seems to be quite a while... or at least longer than a fully charged iPhone will!

Okay this now has exceeded my expectations. I used the charger for 1 and a half hours the first time. Then tonight without recharging it I used it for 3 hours straight and guess what? it's still 3/4 charged. The green light is only slightly diminished!! and my iphone died!! (and it was fully charged when I began!) so...keep posted folks cause this is SWEET!!

We're probably looking at 10-12 hours of use on a single charge! Not bad!

As a bonus, all this tinkering lead Maria to producing a new track using Animoog and NanoStudio.

Koushion is a dedicated MIDI step-sequencer. It looks really cool, even though it lacks Virtual MIDI support. There are a lot of people that feel any synth is improved by the addition of a step-sequencer, so this is a nice way to make that happen!

I tried to review it, but I ran into a couple of show-stopping problems. The first being that I can't use my M-Audio UNO (USB-MIDI adapter) due to the way the Uno is sending clock sync. Bummer. I tried to run a WIFI connection to my computer, but there was some major bug going on with their Windows Koushion MIDI controller software (required proprietary software, it doesn't use rtpMIDI like most apps). The app would be running fine on its own, but as soon as I got a connection to my Windows computer, the iPad app would crash! Every single time, over the course of nearly an hour of testing. It would send notes just fine for a bit, but if I pressed anything on the App screen (like octave shift) it would crap out instantly.

It has been updated, but it doesn't look like it addresses any of my problems.

• Fixed bug with saving channel mappings
• Quantization now takes effect immediately upon resuming stopped playback rather than waiting until the end of a complete sequence

Buy Koushion on iTunes: $9.99

I am assured, by Kudzu Creative Group, that my experience is just a fluke. No one else has reported these crashes, so maybe it is a new bug with iPad 3s.

Here is video evidence from Chris Stack that it does work, and it is kind of awesome when it does!

Nick and Gaz are back with another Sonic Touch episode! I'm so glad they keep doing these! Here are the show notes:

We’re back this episode with a look at Alchemy Mobile from Camel Audio - an impressive sounding synthesizer with a long pedigree on the desktop, now just updated for iOS. Gaz appears to have fallen in love with the wide range of sounds it can offer as a standalone App and the integration with the desktop version is impressive.

Buy Alchemy Synth Mobile on iTunes: Free (Pro Upgrade In-App Purchase $14.99)

There is no explanation for why Cantor is suddenly free, so hurry up and get it while the getting's good! This is Rob Fielding's reincarnation of GeoSynth.

Buy Cantor on iTunes: Free (On Sale, from $2.99)

A Microtonal Guitarist's synth, designed for extreme playability on the iPhone and iPad. It is the successor to Geo Synthesizer and Mugician. It does send a specialized MIDI output (requires a multi-timbral synth that can handle independent channels is all but necessary, such as SampleWiz or ThumbJam in OMNI mode, or Arctic Synth). The internal synth is driven by the actual MIDI output, because external MIDI synths are the main point of this project rather than the internal audio engine. It has a basic looper/delay combination, and the loop can be copied out as a sample to the general pasteboard for apps such as GarageBand.

Thank you very much to Hoyas79 for bringing this sale to my attention!

Update - I just got the following message from Rob on Google Plus (I keep telling you all the cool kids are on there! Facebook is full of people I know, G+ is full of people I want to know.)

I am only selling 3 copies [of Cantor] a day, down from a few hundred in the first few days. So I am doing some experimentation to measure its potential. I had this sort of phenomenon with Mugician, and it hit #4 in free music for the 2 days it first went free.

The plan for now: randomly, when Mugician is free Cantor is for sale. I actually did get lots of requests from heavy Mugician users to pay for Mugician when I was actively developing it. I would like to make it an optionally paid app where users can name the price without getting into maintaining and submitting multiple versions, so I am doing it by simply putting in price variations. 

I really like this idea. It is a kind of "Pay What You Like" model, done in the limitations of the AppStore! Rob is a really clever guy, I have such a nerd-crush for him.

Here's a demo from Rob himself! You may also know him as the guy behind Mugician.

Several people have mentioned that I end up costing them a lot of money; from showing off apps here. In the spirit of sportsmanship:

Run away! Abandon all hope and wallets, ye who enter this article!

As much as we all love to tweak around with things on our iOS screens, for actually playing a keyboard... you want a keyboard! I can't emphasize enough how much more I play now that I set up the SynthStation 61. It is just so much more fun and natural. I tweak the knobs and sliders on the screen and play the notes with the keyboard. Even if you don't have any experience playing a keyboard, you'll get better just by having fun with one.

A couple of iPad specific, 37-key, keyboard reviews have just come out from Kelly's Music & Computers, an online gear retailer. I usually dislike retailer reviews, but I think Kelly does a good job of getting to the stuff that matters to iOS Musicians. I also like that these are 37-keys he's looking at, as that is my personal minimum zone.

First up is the sleek and cheap GarageKey Mini 37. I checked and Kelly actually has the best price on this one, beating Amazon by $10, at just $59 on his company site. If you have small fingers, or a small area you're playing in, then these mini-keys will suit you.

That seems like a nice entry-level option, but I dislike the location of the octave switches. If you want some bigger keys and a bunch of knobs he's got a nice battery-powered solution with the Miditech i2 Control 37. This is $148 on Kelly's site and I can't find it available anywhere else in the US. $250 in New Zealand!