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#2437 SET REVIEW: 21323 Grand Piano 

Alt text / image descriptions are available for the images in this post.

A unique Powered Up set that is System and not a train! With the motion sensor – never before seen outside of education kits – this piano is “almost playable.” Read on to see what we meant by that, and spoilers for pianists: this model has simple escapement and aftertouch!

#2437 SET REVIEW: 21323 Grand Piano A unique Powered Up set that is System and not a train! With the motion sensor – never before seen outside of education kits – this piano is “almost playable.” Does this majestic black box hit the high notes? Let's find out before it retires!  £344.99, $399.99, €399.99 for 3662 pieces. Our score: 23 out of 25.

[Review products provided by the LEGO Group but all opinions are our own and honest – we don’t have to praise sets to keep receiving them. #gifted]

Cover page fold image by starline on Freepik and piano action model image from; chair image from

Parts selection score: 4 out of 5 Some have remained rare or exclusive till now since its 2020 launch; no stickers plus the long axles, flex tubes, and long bricks in bulk make it a solid 3/5 selection. An extra point for  the electronics: the medium motor (€13), the motion sensor (€25), and the hub (€50) have a combined value of about €90 when still listed on, but now only the hub remains and is usually out of stock. This hub (28738) is also the most accessible and compact Pybricks-programmable hub. Here are the rare parts in this set. The part name, colour and quantity are stated for each part. Rare in 0 other sets: Tile 6 by 6 with Bottom Tubes with "PLAYDAY" Music Sheet print, White, x1. Tile Special 2 by 2 Inverted with Gold LEGO print, Black, x1. Hose Rigid 3mm D. 32L / 25.6cm, Pearl Gold, x12. Rare in 2 other sets: Sensor, Motion, We-Do 2.0 2 by 4 by 1, White, x1. Rare in 3 other sets: Brick Curved 1 by 4 by 3, Black, x6. Hose Rigid 3mm D. 26L / 20.8cm, Pearl Gold, x3.

Features score: 5 out of 5 Somewhat unexpectedly, the measurements actually exceed that of a standard 14" laptop. It is also hefty and dense – feels like two modulars when lifting it. Minifigures are but the size of a small plush when set next to this grand piano! The colossal proportion is established early on, with cleverly designed mechanisms filling up the interior, before everything is encased in a smooth curvy box that opens like the real thing. Overall, a very enjoyable and involved build for seasoned builders. The most repetitive part is also the most ingenious – the 25 keys. The majority of the mechanisms and the build overall are system- based, with only very few Technic used to realise the Powered Up functions.

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The adjustable chair is a Technic core cloaked with a studless exterior. The completely upside-down top is connected to the rest by the scissors lift, and bears a remarkable resemblance to real leather cushions. Adjust the height by turning the knob on either side – just like the real thing.

A video showing the height adjustment in action.

A picture of real piano chairs for comparison.

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The removable and openable parts of a real piano are all present and function similarly. Only the right pedal has function though. Pieces with round edges to guide the inserts. The hatch on the side is to access the Powered Up hub and activate the electronic functions.

A video showing its modularities.

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The Powered Up app is required, since it's your own device playing the sound thru Bluetooth connection to the hub.

In the LISTEN mode, the keys move in a fixed pattern automatically by the motor (not corresponding to the actual music played). The sound of the motor is still too loud for a reasonable player piano though. 20 musical pieces available.

In the PLAY mode, the rhythm can be controlled by the keys (with slight delay), but not the pitch, the duration, nor the dynamics. 9 musical pieces available.

Since the next correct note plays regard-

less of the key hit, anyone can “play.” You can also choose to press the right keys yourself.

A video demonstrating the PLAY mode using “twinkle twinkle little star.”

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Techniques score: 5 out of 5

3 long axles span across the width, making functions work: the first two bob, and the 3rd one is driven by the motor to rotate and move the keys when in LISTEN mode. In PLAY mode, when a key is pressed, the 1st axle is lifted by the lever along with the dampers above. This moves the red half beams into the vision of the sensor so the app plays a note.

A picture showing the location of the 3 axles mentioned.

A video showing how a key raises the damper and the 1st axle.

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The dampers can be lifted one by one through the lever of the corresponding key, or all at once by the rightmost pedal through linkage. A 1x2x2 window provides the opening for the linkage to go through.

A video showing the pedal raising the dampers all at once.

The satisfying soft close lid is achieved by simply using friction pins in combination with the appropriate weight for the lid.

A video showing the soft close lid.

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Accuracy score: 5 out of 5

Key: a long brick balancing on an upside-down ice cream cone and supported by curved bricks. This allows it to move, throw the free-moving hammer with the brown pin hole on top to hit the string, and lift the damper with the red tile in the back when pressed down.

Impressive recreation of the “touch”: when pressed slowly, we see it’s the final jerk that propels the hammer to strike suddenly. This is possible due to the extra height of the connector lip for the pin hole to overcome.

A video showcasing how the a is put on to the ice cream cone element, and how it propels its corresponding hammer.

In auto-play, the motor rotates the 3rd axle and the beams to move the key.

Value for money score: 4 out of 5 The RRP increased from €350 to €400 in Sept 2022. The 10.9c price per part is especially misleading given the electronic components; instead, we compared it to similar sets like the Motorized Lighthouse (14.5c). Excluding electronics, it beats the similarly functional IDEAS Typewriter, which is 80% of the price for 56% of the parts. Unlike the Holiday Main Street tram, electronics are critical to the interior build and couldn't be sold separately. A photo showing its scale next to the Rivendell set. It is wonderful such a polished and accurate model exists, pushing LEGO’s system and technology to the limit. The mechanism is top-notch, the electronics well- integrated, but the in-app music does not have corresponding scores and sounds computer generated – for the new Sound Design department to improve upon!


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