Sadly clothes are pretty bad at learning new musical instruments. 
Therefore i came up with a quick fix that will at least expose them to piano keys and hopefully raise their willingness to learn.

The black #-Keys are designed to snap into open and closed positions so if no clothes are hanging it can be transformed to look like a real piano octave.

Print Instructions

Print settings used for all parts (Matte PLA - Extrudr NX2):

Layer height of .2mm, 5 top and bottom layers, 10% gyroid infill otherwise default prusa slicer structural settings. 
Also a .4 Nozzle was used.

White Keys:

To get a nice surface finish on the White Keys (C, D, E, F, G, A, H) i recommend to turn them upside down in the slicer (so the top is now on the bottom of the plate).

(Keep in mind that the Holes for the Connectors are not located in the center of the key)

Black # Keys (Hooks, Print 5 of these):

Imho best looking when printed sideways as then there is no different surface finish on the top of the key. (Also i assume it is best stability wise.)

Connectors (Holder for Hooks, Print 5 of these):

Printed vertical without Brim. (a brim can be added tho)

Octave Box:

Print orientation should be obvious (surface facing the wall should be on the build plate).

Assembly Instructions

Things required for this step: 
- Your favorite type of glue (don't sniff too long, read the instructions first)
- All parts already printed out

Start with gluing the Key-Groups together separately first, beginning with the C,D,E Keys:

• Glue one of the connectors in the C-Key (let it dry), put on the #-Key (Hook) with the rounded side facing the open direction of the white keys.
• After that put some glue in the hole of the D-Key and place this and the previously glued key on a flat surface and put them together (Try to move around the white keys so they are aligned and there is a small gap between C and D (ideally .8mm) before the glue dries.
• Do the same procedure for the E-Key as well as the other Key-Group.
• After that turn around the groups and put glue on all white keys, then insert them into the Octave-Box and space them out evenly again (This can be a bit of a hassle if you want perfect spacing and alignment of the keys since print and gluing tolerances might not be your friend here, and the snap mechanism restricts you from moving the key groups freely)
• In case you have managed to glue your hand onto the plastic parts, congratulations you can now cut-off your hand and grow a new one (in case your hand can't do that try something else - i am out of ideas here)
• If you have finished the assembly and regrew your hand, you can now continue to sniff your glue (or don't, i wont judge here)

Mounting instructions

Things required for this step:
- 1x water level or a leveling laser in case you are rich and want to destroy your eyes by doing a staring contest with this little creature.
- 1x pencil (IKEA pencils are great for this)
- 1x hammer drill or similar with a drill 6mm in diameter (check whether your walls are out of cardboard or bricks and adjust accordingly)
- 5x dowels for 4-5mm screws (which in my case were 6mm dowels) (type also may vary on the type of wall, for the Berlin wall i would recommend dowels from fischer, for the wall of the mexico-us-border i highly advise against dowels and drilling since it is actually a large fence - please don't drill into any walls if you do not own them or are authorized to by the owner)
- 5x screws 4-5mm in diameter (i used 4mm) (screw-length should not  exceed the length of the dowel by much, at this point you may remember and tell everyone who is standing by that length is not that important for mounting but diameter is)

• flip the hooks so the boreholes are accessible for the pencil.
• use the water- or laser-level to position the case at the height you prefer.
• use the pencil to mark the hole positions (start with the outer positioned holes)
• drill the holes (keep in mind you have to be precise here as i did not add any vertical space to adjust height later to level things out, i left it out due too cosmetic reasons and a bit of laziness. If you think that would be a good improvement, please let me know)
• hammer in the dowels
• hold the printed item onto the holes to check if you have ****ed up. In case you did not, great job, you can now use the screws to attach the whole thing on the wall.

Congratulations you have successfully read this way too long tutorial. 
And hopefully you also equipped your wardrobe with some learning utensils.

Give your clothes a few months to hang on it before taking them to a public space with a piano so they can earn money and compensate for all the time and material you have spent on this.

Thank you for reading this far and let me know in case anything can be improved.