High-resolution promotional campaign for major release
At a time when all bugs are fixed and features implemented for a major version in the future (not currently known which), there could be a special one-off campaign to promote it - reserved for a time everyone is confidant about the software's presentation (design, features and stability). One such idea is internet adverts (also through other mediums perhaps) roughly a fortnight prior to release. It would introduce the software to many.
As soon as development is deemed complete by the team, we could invite people (members or otherwise) to test it and give their opinions. Once amended and approved, it can be released - rather similar to the Apple Developer's Program.
After the release, we could ask reviewers and users to assess it and give opinions. Anything raised could be used towards improving the next version.
Although traditional engravers would appreciate the below adverts, they may not appeal to non-classical users. Perhaps two (maybe more, depending) separate adverts could be made, targeting each market. The classic version (manuscript orientated) would bare more maturity, whilst the guitarist version (tablature) would look slightly more like an iPod advert (although we must be careful not to abandon professional users of this side either).
These would look corporate-like, and understated too (leaving viewers wanting to know more). For YouTube, the adverts would be 1080p - other websites would most likely be different in specifications (e.g. long, horizontal or vertical banner versions).
After the release, there could be general adverts - not necessarily films, but banners.
This could be used before presenting certain (not all perhaps) videos.
On the subject of visual adverts, there could also be a website introduction when you go to musescore.com.
This list is just for initialisation and isn't finalised - feel free to discuss.