transform keys and text service

src/app/modules/songs/song/edit/edit-song/edit-song.component.html

@@ -16,7 +16,7 @@
       <mat-form-field appearance="outline">
         <mat-label>Tonart</mat-label>
         <mat-select formControlName="key">
-          <mat-option *ngFor="let key of keys" [value]="key">{{key}}</mat-option>
+          <mat-option *ngFor="let key of keys" [value]="key">{{key|key}}</mat-option>
         </mat-select>
       </mat-form-field>
       <mat-form-field appearance="outline">