Affordances and Constraints

Note-taking for User Experience Design with June Ahn

Don Norman discusses affordances and constraints in The Design of Everyday Things, Chapter Four: Knowing What To Do.

Don Norman - The Design of Everyday Things

User experience design is easy in situations where there’s only one thing that the user can possibly do. But as the possibilities multiply, so do the challenges. We can deal with new things using information from our prior experiences, or by being instructed. The best-designed things include the instructions for their own use, like video games whose first level act as tutorials, or doors with handles that communicate how you should operate them by their shape and placement.

We use affordances and constraints to learn how things work. Affordances suggest the range of possibilities, and constraints limit the alternatives. Constraints include:

  • Physical limitations. Door keys can only be inserted into keyholes vertically, but you can still insert the key upside down. Car keys work in both orientations.
  • Semantic constraints. We know that red lights mean stop and green lights mean go, so we infer that a red light means a device is off or inoperative, and a green light means it’s on or ready to function. We have a slow cooker that uses lights in the opposite way and it screws me up every time.
  • Cultural constraints. Otherwise known as conventions. (Not sure how these are different from semantic constraints.) Somehow we all know without being told that we’re supposed to face forward in the elevator. Google Glass was an epic failure because its early adopters ran into the cultural constraint of people not liking to be photographed without consent.
  • Logical constraints. The arrangement of knobs controlling your stove burners should match the arrangement of the burners themselves.

The absence of constraints makes things confusing. Norman gives examples of how much designers love rows of identical switches which give no clues as to their function. Distinguishing the switches by shape, size, or grouping might not look as elegant, but would make it easier to remember which one does what thing.

Helpful designs use visibility (making the relevant parts visible) and feedback (giving actions an immediate and obvious effect.) Everyone hates the power buttons on iMacs because they’re hidden on the back, flush with the case. Feedback is an important way to help us distinguish the functional parts from the decorative ones. Propellerheads Reason is an annoying program because its skeuomorphic design puts as many decorative elements on the screen as functional ones. Ableton Live is easier to use because everything on the screen is functional.

When you can’t make things visible, you can give feedback via sound. Pressing a Mac’s power button doesn’t immediately cause the screen to light up, but that’s okay, because it plays the famous startup sound. Norman’s examples of low-tech sound feedback include the “zzz” sound of a functioning zipper, a tea kettle’s whistle, and the various sounds that machines make when they have mechanical problems. The problem with sound as feedback is that it can be intrusive and annoying.

The term “affordance” is the source for a lot of confusion. Norman tries to clarify it in his article “Affordance, Conventions and Design.” He makes a distinction between real and perceived affordances. Anything that appears on a computer screen is a perceived affordance. The real affordances of a computer are its physical components: the screen itself, the keyboard, the trackpad. The MusEDLab was motivated to create the aQWERTYon by considering the computer’s real affordances for music making. Most software design ignores the real affordances and only considers the perceived ones.

Designers of graphical user interfaces rely entirely on conceptual models and cultural conventions. (Consider how many programs use a graphic of a floppy disk as a Save icon, and now compare to the last time you saw an actual floppy disk.) For Norman, graphics are perceived affordances by definition.

Joanna McGrenere and Wayne Ho try to nail the concept down harder in “Affordances: Clarifying and Evolving a Concept.” The term was coined by the perceptual psychologist James J. Gibson in his book The Ecological Approach to Visual Perception. For Gibson, affordances exist independent of the actor’s ability to perceive them, and don’t depend on the actor’s experiences and culture. For Norman, affordances can include both perceived and actual properties, which to me makes more sense. If you can’t figure out that an affordance exists, then what does it matter if it exists or not?

Norman collapses two distinct aspects of design: an object’s utility of an object and the way that users learn or discover that utility. But are designing affordances and designing the information about the affordances the same thing? McGrenere and Ho say no, that it’s the difference between usefulness versus usability. They complain that the HCI community has focused on usability at the expense of usefulness. Norman says that a scrollbar is a learned convention, not a real affordance. McGrenere and Ho disagree, because the scrollbar affords scrolling in a way that’s built into the software, making it every bit as much a real affordance as if it were a physical thing. The learned convention is the visual representation of the scrollbar, not the basic fact of it.

The best reason to distinguish affordances from their communication or representation is that sometimes the communication gets in the way of the affordance itself. For example, novice software users need graphical user interfaces, while advanced users prefer text commands and keyboard shortcuts. A beginner needs to see all the available commands, while a pro prefers to keep the screen free of unnecessary clutter. Ableton Live is a notoriously beginner-unfriendly program because it prioritizes visual economy and minimalism over user handholding. A number of basic functions are either invisible or so tiny as to be effectively invisible. Apple’s GarageBand welcomes beginners with photorealistic depictions of everything, but its lack of keyboard shortcuts makes it feel like wearing oven mitts for expert users. For McGrenere and Ho, the same feature of one of these programs can be an affordance or anti-affordance depending on the user.

Project-based music technology teaching

I use a project-based approach to teaching music technology. Technical concepts stick with you better if you learn them in the course of making actual music. Here’s the list of projects I assign to my college classes and private students. I’ve arranged them from easiest to hardest. The first five projects are suitable for a beginner-level class using any DAW–my beginners use GarageBand. The last two projects are more advanced and require a DAW with sophisticated editing tools and effects, like Ableton Live. If you’re a teacher, feel free to use these (and let me know if you do). Same goes for all you bedroom producers and self-teachers.

The projects are agnostic as to musical content, style or genre. However, the computer is best suited to making electronic music, and most of these projects work best in the pop/hip-hop/techno sphere. Experimental, ambient or film music approaches also work well. Many of them draw on the Disquiet Junto. Enjoy.

Tristan gets his FFT on


Assignment: Create a song using only existing loops. You can use these or these, or restrict yourself to the loops included with your DAW. Do not use any additional sounds or instruments.

For beginners, I like to separate this into two separate assignments. First, create a short (two or four bar) phrase using four to six instrument loops and beats. Then use that set of loops as the basis of a full length track, by repeating, and by having sounds enter and exit.


  • Basic DAW functions
  • Listening like a producer
  • Musical form and song structures
  • Intellectual property, copyright and authorship


  • MIDI loops are easier to edit and customize than audio loops.
  • Try slicing audio loops into smaller segments. Use only the front or back half of the loop. Or rearrange segments into a different order.

final song


Assignment: Create a piece of music using MIDI and software instruments. Do not record or import any audio. You can use MIDI from any source, including: playing keyboards, drum pads or other interfaces; drawing in the piano roll; importing scores from notation programs; downloading MIDI files from the internet (for example, from here); or using the Audio To MIDI function in your DAW. 

I don’t treat this as a composition exercise (unless students want to make it one.) Feel free to use an existing piece of music. The only requirement is that the end result has to sound good. Simply dragging a classical or pop MIDI into the DAW is likely to sound terrible unless you put some thought into your instrument choices. If you do want to create something original, try these compositional prompts.


  • MIDI recording and editing
  • Quantization, swing, and grooves
  • “Real” vs “fake” instruments
  • Synthesized vs sampled sounds
  • Drum programming
  • Interfaces and controllers


  • For beginners, see this post on beatmaking fundamentals.
  • Realism is unattainable. Embrace the fakeness.
  • Find a small segment of a classical piece and loop it.
  • Rather than playing back a Bach keyboard piece on piano or harpsichord, set your instrument to drums or percussion, and get ready for joy.

Montclair State Music Tech 101

Found sound

Assignment: Record a short environmental sound and incorporate it into a piece of music. You can edit and process your found sound as you see fit. Variation: use existing sounds from Freesound.


  • Audio recording, editing, and effects
  • The musical potential of “non-musical” sounds


  • Students usually record their sounds with their phones, and the resulting recording quality is usually bad. Try using EQ, compression, delay, reverb, distortion, and other effects to mitigate or enhance poor sound quality and background noise.

pyt stems

Peer remix

Assignment: Remix a track by one of your classmates (or friends, or a stranger on the internet.) Feel free to incorporate other pieces of music as well. Follow your personal definition of the word “remix.” That might mean small edits and adjustments to the mix and effects, or a radical reworking leading to complete transformation of the source material.

There are endless variations on the peer remix. Try the “metaremix,” where students remix each others’ remixes, to the nth degree as time permits. Also, do group remix activities like Musical Shares or FX Roulette.


  • Collaboration and authorship
  • Sampling
  • Mashups
  • Evolution of musical ideas
  • Musical critique using musical language


  • A change in tempo can have dramatic effects on the mood and feel of a track.
  • Adding sounds is the obvious move, but don’t be afraid to remove things too.

Self remix

Assignment: Remix one of your own projects, using the same guidelines as the peer remix. This is a good project for the end of the semester/term.

Song transformation

Assignment: Take an existing song and turn it into a new song. Don’t use any additional sounds or MIDI.


  • Advanced audio editing and effects
  • Musical form and structure
  • The nature of originality


  • You can transform short segments simply by repeating them out of context. For example, try taking single chords or lyrical phrases and looping them.


Shared sample

Assignment: Take a short audio sample (five seconds or less) and build a complete piece of music out of it. Do not use any other sounds. This is the most difficult assignment here, and the most rewarding one if you can pull it off successfully.


  • Advanced audio editing and effects
  • Musical form and structure
  • The nature of originality


  • Pitch shifting and timestretching are your friends.
  • Short bursts of noise can be tuned up and down to make drums.
  • Extreme timestretching produces great ambient textures.

Mobile music at IMPACT

Writing assignments

I like to have students document their process in blog posts. I ask: What sounds and techniques did you use? Why did you use them? Are you happy with the end result? Given unlimited time and expertise, what changes would you make? Do you consider this to be a valid form of musical creativity?

This semester I also asked students to write reviews of each others’ work in the style of their preferred music publication. In the future, I plan to have students write a review of an imaginary track, and then assign other students to try to create the track being described.

The best way to learn how to produce good recordings is to do critical listening exercises. I assign students to create musical structure and space graphs in the spirit of William Moylan.

Further challenges

The projects above were intended to be used for a one-semester college class. If I were teaching over a longer time span or I needed more assignments, I would draw from the Disquiet JuntoMaking Music by Dennis DeSantis, or the Oblique Strategies cards. Let me know in the comments if you have additional recommendations.