I have been exploring design possibilities for a 32-note MIDI driven
"crank organ" for several years.  Part of my design concept involves
using a small tablet computer to play MIDI files through a 32-note
MIDI-to-parallel circuit board.

Over a year ago I bought an Android tablet, but I was never able to
find playback software which would link to a MIDI keyboard for playback
through one of the cheap USB to MIDI devices.  I believe that others
have tried this approach, but no one has reported a success.

I have been waiting for the price to drop on Windows tablets.  A couple
of days ago I received a Wal-Mart ad for the Nextbook Flexx 10 at $100
plus tax, and I took the plunge.  (Nextbook Flexx 10.1" 2-in-1 Tablet
2/32GB Quad Core Windows 8, Eligible for Free Windows 10 Upgrade.)

This is a closeout on the Win 8.1 model, and the price seems to
bounce up and down.  This model has a removable keyboard, allowing use
in either tablet or notebook mode.  The 10-inch diagonal size of the
tablet should make it feasible to build a holder for it directly into
the organ case.  You will want to buy a tablet stylus at your 'dollar
store' to help you deal with the small screen size.

The USB-to-MIDI link I used has two silver MIDI cables and a USB cable
connected through a small black box.  The box has a power light and IN
and OUT lights, and a sloppy-tilted treble clef sign on a mini-score,
but no indication of brand or manufacturer.  These devices have had a
mixed reputation for quality, but they cost less than $4 if purchased
directly from Chinese vendors.  Mine looks like the one on eBay at
http://www.ebay.com/itm/201416064081 

You will need a Micro USB to USB adapter (about $2 from China).  I had
two on hand and one worked, and one didn't.

I connected it to a MIDI keyboard which I have had for about 20 years
for test purposes.  When I connected the cable the Nextbook was
connected to the web, and the driver installation followed without
problems.  This may, or may not, be important.

I installed my regular MIDI editing program, PowerTracks Pro 2013,
loaded a file, and it played properly after setting the cable as the
output device.

My choice of PowerTracks for playback is based on the ability to
use it in "piano roll" display mode.  I will want to be able to say
"I'm actually playing music rolls, they are just on digital paper.
A PDF file is a paperless document and a MIDI file is a paperless organ
book or roll."

I think a good many other Windows tablets will also work, and that
Win 10 will work as well as Win 8.1, but I have only tried this one.
I haven't had time to wring the system out thoroughly, driving out
MIDI organ, using Windows Media Player, testing several cables, etc.,
but I am excited to be able to say a low-cost, high resolution,
solution is now in hand.

Wallace Venable

 [ PowerTracks Pro Audio 2015 is described and sold at
 [ http://www.pgmusic.com/powertracks.htm  -- Robbie