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MIDI Loopback Driver

Introduction

The MIDI Loopback driver is a virtual driver that allows you to capture MIDI events from any MIDI sequencer that plays MIDI files.

Configuration

  • Run soundconf, configure the soundcard and then select "Add new card or device" option. Then select the "4Front Technologies MIDI Loopback" device from the list of available devices.
  • Now run soundon and type cat /dev/sndstat - you will get 2 additional devices under the "MIDI Devices" heading marked as "MIDI loopback" and "MIDI loopback server side". 
    Card config: 
VIA 8233 AC97 audio controller at 0xe800 irq 11
MIDI loopback driver

Audio devices:
0: VT8233 (DUPLEX)
1: VT8233 (shadow) (DUPLEX)
2: OSS Virtual Mixer v2.5 Playback CH #0 (GRC3)
3: OSS Virtual Mixer v2.5 Playback CH #1 (GRC3)
4: OSS Virtual Mixer v2.5 Playback CH #2 (GRC3)
5: OSS Virtual Mixer v2.5 Playback CH #3 (GRC3)
6: OSS Virtual Mixer v2.5 Playback CH #4 (GRC3)
7: OSS Virtual Mixer v2.5 Playback CH #5 (GRC3)
8: OSS Virtual Mixer v2.5 Playback CH #6 (GRC3)
9: OSS Virtual Mixer v2.5 Playback CH #7 (GRC3)

Synth devices:
0: OSS Virtual Synth v2.5

Midi devices:
0: MIDI loopback
1: MIDI loopback server side

Mixers:
0: VT8233 (ALC650)
1: Virtual Mixer

Testing MIDI Loopback device

Type: od -x /dev/midi01 (or the device number of the "server side" loopback device. Now you can play midi files to the loopback device by typing ossmplay 1 where 1 is the device number of the "client side" loopback device (if you type ossmplay and press enter it will show you what MIDI devices are available so you need to select the number of the "MIDI loopback device". You will now see the output from od -x /dev/midi01 which is basically capturing MIDI events from the ossmplay program (or it can be any sequencer application). 

0000000 50c0 07b0 0a7f c114 b121 7f07 53c2 07b2
0000020 0a7b c332 b319 7f07 4d93 c45f b431 7307
0000040 280a 57c5 07b5 c67c b603 6c07 460a 37c7
0000060 07b7 977b 7f41 734d 57c8 07b8 b970 7f07
0000100 2499 317f 2a7f 4376 ca5a ba79 7f07 79ca
0000120 07ba 997f 0043 0024 0031 002a 4d93 4d00
0000140 994e 732a 002a 4d93 4d00 994e 702a 7f27
0000160 5a43 0043 0027 002a 4d93 4d00 994e 6c2a
0000200 002a 4d93 4d00 995f 7f24 762a 7f27 7f26
0000220 5a44 0044 0027 0024 002a 0026 4d93 4d00

Applications of MIDI Loopback

With the MIDI loopback driver, you can essentially use any wave-table synthesizer and then have a sequencing application use that synth to play MIDI data you input in the sequencer.