• # Lesson 2. Introducing OMN

## Annotation

This script looks almost the same as the first. And it sounds the same! But there are important differences. First, this expression has changed.

`(setf lengths (span pitches '(e)))`

The 1/8 has become e. This is an eighth note-length in Opusmodus Notation (OMN).

```(setf piano-righthand
(make-omn
:length lengths
:pitch pitches
:velocity dynamics))

(setf piano-lefthand
(make-omn
:length lengths
:pitch transposed-pitches
:velocity dynamics))```

This function MAKE-OMN turns the parametric output of length, pitch and velocity into a single script of Opusmodus Notation (OMN).

So piano-righthand becomes:

`(e c4 p cs4 mp fs4 mf g4 f c5 ff)`

and piano-lefthand becomes:

`(e c3 p cs3 mp fs3 mf g3 f c4 ff)`

This is the preferred way of putting together the parameters that combine to make a musical phrase. It will gradually become obvious why we do this as this guide continues. It does make defining the score more concise:

```(piano-rh
:omn piano-righthand
:channel 1
:sound 'gm
:program 'acoustic-grand-piano)```

## Score

```(setf pitches '(c4 cs4 fs4 g4 c5))
(setf transposed-pitches (pitch-transpose -12 pitches))
(setf lengths (span pitches '(e)))
(setf dynamics '(p< < < < ff))

(setf piano-righthand
(make-omn
:length lengths
:pitch pitches
:velocity dynamics))

(setf piano-lefthand
(make-omn
:length lengths
:pitch transposed-pitches
:velocity dynamics))

(setf timesigs (get-time-signature lengths))

(def-score lesson-2
(:key-signature 'chromatic
:time-signature timesigs
:tempo 80
:layout (piano-layout 'piano-rh 'piano-lh))

(piano-rh
:omn piano-righthand
:channel 1
:sound 'gm
:program 'acoustic-grand-piano)

(piano-lh
:omn piano-lefthand)
)```

## Notation

Next page Lesson 3. Defining Chords

Go back to Reference page.

Edited by opmo

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