Writing with intentional limitations

Recently I've discovered a project undertaken by the Schubert Ensemble of London in conjunction with a number of (mostly British) composers called "Chamber Music 2000," which has currently produced two albums' worth of music and a small amount of music education material. The idea is that the Ensemble commissions brief pieces for piano and strings from composers, who are expected to write "at the easiest technical level for which they feel able to write, while still preserving the integrity...of their musical language". This way, young musicians get a chance to perform and listen to new works by established professional composers.

The implications of the project as it relates to the welfare of young musicians notwithstanding, I think it's an interesting idea to write these sorts of pieces as much more than just teaching material: has anyone here ever intentionally written a relatively easy piece not expressly for the purpose of writing an easy piece, but as an exploration of their own musical language and ideas? Tell us about it, and how you went about doing so.

I thinkk it is a good approach towards composing. Idea of intentional limitation is not new: for example, there was Oulipo - a group of writers in France who used constrained writing techniques. So one could have expected it in music, and moreover: a key is also a limitation in its own way, which means basically all music is somewhat restrained (including atonal which is restrained by being atonal, i.e. it has at least one rule to follow). The only difference is to what extent do you limit it; to my view, the lesser space for maneuvers you have, the more original your music may be - you have to invent workarounds to do simple things instead of walking the beaten path, and the results are completely different from what you're used to.