[LAU] Musical Score Editors - some advice for beginners

[Pedro Lopez-Cabanillas]

On Thursday, September 24, 2009, Emiliano Grilli wrote:
> Werner Schweer <ws at seh.de> writes:
> > MuseScore is still being developed.
>
> I'm trying version 0.9.5 and I find it a really nice
> application. Although I'm not that confindent with written music, I'm
> willing to learn: and musescore has a great appeal in this regard.
>
> However, I'm not able to connect it with external MIDI synthesizers. I
> see alsa  midi ports but nothing seems to pass through them (tried
> with kmidimon). If I select to use the MIDI out in the preferences the
> song won't start at all, while with the internal synth all is working
> good.
>
> Any hints on this problem?

When you start KMidimon first, and then you start MuseScore from a terminal 
session, you can see the following messages:

$ mscore
RtcTimer:: fatal error: open /dev/rtc failed: Device or resource busy
MidiSeq:start(): no midi timer available
Cannot start I/O
sequencer init failed

This happens because KMidimon creates an ALSA Sequencer queue, and ALSA uses 
the RTC device for their own sequencer, so mscore finds that it is busy when 
tries to open it. The same happens if you start arecordmidi before mscore, or 
any other program that uses ALSA sequencer queues. 

You can use aseqdump instead of KMidimon to monitor the MIDI events coming 
from mscore, because aseqdump doesn't display the event's timestamps so it 
doesn't need to use a queue. You can also start MuseScore first, and KMidimon 
later. Or tell the ALSA sequencer to use a different timer source by default. 
These are not real solutions, only workarounds. The solution would be to   
implement an ALSA timer in MuseScore, or even better: use the ALSA sequencer 
scheduling services instead of an internal timer. 

I would like to contribute with code to solve this, because I like many of the 
program features, but the project leader says that he is going to drop ALSA  
replacing it with Jack MIDI, so implementing better ALSA support for this 
project would be losing the time.

Regards,
Pedro