To create musical content, you first need to set up a project, which will be used for saving files in the workspace. This project needs a distinctive name. Choose from menu File → New → Project or click the corresponding button in the toolbar.

After the creation of a project choose again from menu File → New and then Other…. In the opening dialogue box choose MEI documents → MEI music encoding and click Next.
Pick the project you named before and give a name to the MEI file. Choose the number of staves and measures → click Finish and the file will open with an empty staff/measure depending on your input.
The Project Explorer on the left side of MEISE indicates the saved files, which could be easily opened by double-clicking on them. You can create multiple Projects to store your MEI files.
Opening an MEI-file in MEISE allows to modify the content by using the Outline- and Properties View. The following example demonstrates adding a slur in an existing file and subsequent modifying the attributes for describing the slur. First, it is required to drag the slur-element of the Palette into the Outline-View.
After that, the slur needs a more detailed definition concerning start- and endpoint as well as duration and form. Therefore the Properties View should be used. Click the appropriate element in the Outline and the slur will appear in the Properties View. Over there, the attributes could be defined by there values for curve direction (above or below), startid and endid (copied from the appropriate notes) and if necessary a timestamp.
The slur will appear after clicking "enter" in the Musical Score View. By modifying the value of the curve direction, the slur will change its position immediately.
The XML-structure of the new file could be opened in an XML-Editor (e.g. oXygen XML Editor) or in the simple text view perspective within the MEISE. Installation tips for including an XML Editor within MEISE can be found under [Quick Start].
MEISE provides the opportunity to handle digital representations of musical variants. While using the MEI apparatus with its reading elements it is possible to switch between the note rendering of these different variants in the Editor View. First, it is necessary to declare sources containing the readings. Clicking the "Manage Sources" button in the toolbar of the MEISE will open a new dialog, where the sources can be created with names, labels and annotations like scribal abbreviations. Clicking the close button will save the sources. If there is an MEI-file including variants, the app and reg elements will appear in the Outline View. If you wish to insert those, you may click on the appropriate element in the Palette and drop it in the Outline View and define values of attributes within the Properties View. Keep in mind, that app and reg elements are interacting elements.

To define relations between a reading variant and its corresponding source, click on a "reading"-element in the Outline View and then open the value of its property "Rdg Sources" in the Properties View. A new dialog will open and one or more of the previously declared sources can be selected by clicking "Add sources". Clicking the close-button will save the changes.

To view a particular source's reading variant in the Editor View select the desired source by clicking on the source selection button in the Outline View.

This will switch the Editor and Outline View to render, respectively show all reading variants connected with the source selected. Corresponding elements in the Editor View will be hightlighted in red color, while all active reading variants in the Outline View will be marked in green.
In case of working with MEI-files which already include several sources, every single source has to be associated with the corresponding instances in MEISE although they are declared in the MEI-file. It is important to ensure a correct encoding with declared sources in the MEIHead/sourceDesc, relating to the apps and readings in the music. By managing the sources correctly, MEISE provides the opportunity to switch between the sources in a fast and comfortable way.
<sourceDesc>
<source n="1" label="Source_A" xml:id="Source_A">
<source n="2" label="Source_B" xml:id="Source_B">
<source n="3" label="Source_C" xml:id="Source_C">
</sourceDesc>
<measure>
<staff>
<app>
<rdg n="1" source="Source_A">
<layer>
<note pname="g" oct="4" dur="4"/>
</layer>
</rdg>
<rdg n="2" source="#Source_B">
<layer>
<note pname="a" oct="4" dur="4"/>
</layer>
</rdg>
<rdg n="3" source="#Source_C">
<layer>
<note pname="a" oct="4" dur="2"/>
</layer>
</rdg>
</app>
</staff>
</measure>