[Techtalk] MIdi, QjackCtl etc.

[David Sumbler]

I wonder if somebody can point me in the right direction for sorting out
a midi system.  Search as I might, I can't seem to find any *basic*
information about how to set things up, or how things fit together.

What I want to be able to do ultimately is to input music from an
electric piano with Midi in/out capability, and then edit it.

I have read
https://rafalcieslak.wordpress.com/2012/08/29/usb-midi-controllers-and-making-music-with-ubuntu/
and other even less helpful (to me) articles on line.

I installed QjackCtl as well as Muse and Qtractor - I thought I would
try both the last two and see which one I preferred.

I reckoned that the first thing I should do was to make sure I could
play music from Muse and/or Qtractor through the computer's speakers.
With both programs, and on 2 different computers (both running Ubuntu
12.04) I have loaded existing Midi files (produced by Lilypond) which I
know play perfectly well using Timidity.

But I get no sound at all.  Although I have exactly the same software
(including jackd) on both computers, I get slightly different error
messages from QjackCtl.  Both computers, though, report "Cannot lock
down 82246176 byte memory area (Cannot allocate memory)".

To be honest, I don't even really understand what jackd does - I simply
know that it seems to be required.

If anyone can point me to some basic information on how all this might
be made to work (or even offer advice directly), I shall be very
grateful indeed!

David