---

Topics

Using midi output with Midishare and msOMSDriver

Functions used

pitchwheel, pgmout, repeat-n and CHORD-SEQ.

Introduction

OpenMusic outputs MIDI data thru Midishare or OMS drivers. It can play an external device such as an expander, and may also receive midi data from a controller. In this tutorial we will see how to play MIDI internally via Midishare or OMS or thru an external device.

When OM is launched all drivers in the 'MidiShare Folder' located at the root of your 'System Folder' are automatically launched at MidiShare wakeup time (except those in the 'Disabled folder') . If msOMSDriver is found in this folder, you will have the possibility to use OMS via Midishare.

 

First of all one must set each port in the OM Preferences (in the OM File menu).

 

• Click on Midishare's icon (second icon on the left side of the Preferences dialog box.

• Click on msDrivers icon above to open the Drivers Manager panel.

• Here you are presented with the available input and output drivers, and 256 ports numbered from 0 to 255.

• In order to assign a driver to a port, one must select the driver then choose a port (or vice-versa). So, let us select first the QuickTime GM driver and the port n° 0. The contour of the dialog box will turn red.
• Now close the Driver Manager window
• Reopen it

• The blue colored square is the assigned port. All other squares are free.
• In order to see which device is affected to a given port, select an input or output slot. The corresponding ports will turn green.

• Now drag the mouse curser on the green port. On the center bottom of the panel will appear the corresponding port number.

• In order to play OM musicl factories through a given port, you must specify the desired input or output ports following the configuration made

Now let us examine a patch using QuickTime GM Synth

A: Input some program changes in the list A. These correspond to General MIDI instruments.

B: Input the Channel number for each instrument. Notice that we avoid using channel 10 which is reserved for percussion instruments.

C: pgmout once evaluated will send these program changes to the designated port in its third input (D). This function always returns nil in the Listener. It only sends midi messages.

E: Now input some midicents in the list E and connect list B to the seventh input of CHORD-SEQ (F). This argument will assign for each note a midi channel. Evaluate the CHORD-SEQ object and open its editor.

You can notice that for each note we have a different channel as it is the case of a 'Klangfarbenmelodie'. If you play the CHORD-SEQ, each note will play a different instrument. That is because we have assigned to each channel a different program change with pgmout.

G: Now if you want all the notes to play the piano instrument , evaluate the pgmout (G) which will reset the program changes of all channels we have modified.

B.Playing microtones using pitchwheel

Now let us build a simple patch that will play microtones using CHORD-SEQ.

• We will first use arithm-ser to create a series of midicents ranging from 0 to 200 with a 25 midicent step representing 1/8th of a tone.

• We will add 6000 midics by using om+ to each element of the list (0 25 50 75 100 125 150 175 200) returned by arithm-ser giving a chromatic scale from C3 to D3 in1/8th of a tone. This will return (6000 6025 6050 6075 6100 6125 6150 6175 6200).

• In order to view microtones one must select in the pop-up menu the desired resolution (1/2 for semitones, 1/4 for quarter tones and 1/8 for eightones).

• You will notice if you play the CHORD-SEQ before sending pitchbend messages that all notes falling in a non-tempered scale (quarter and eight notes) will be skipped. That is because OpenMusic automatically maps microtones to other midi channel. Now if we suppose that our original CHORD-SEQ (and it is the default value) was evaluated with channel one for all notes, OpenMusic will automatically map:

• We will send pitchbend valuesfor every channel as follows using the first upper pitchwheel function:

0 to channel 1 which stands for no pitch bend

1024 to channel 2 which stands for one eight tone

2048 to channel 3 which stands for one quarter tone

3072 to channel 4 which stands for one eight + quarter tone.

• The CHORD-SEQ will correctly play the microtones.

For further information concerning Midishare please consult midishare's documentation