It may be difficult to fathom with the hullabaloo going on about Twitter, but people bought music before the service launched. In fact, people bought music before the existence of email, the Internet browser, MySpace, the eight-track cassette and FM radio. It’s best to remember there are other ways, and frequently more effective ways, to communicate with fans.

TechCrunch has a post on musicians’ use of Twitter and provides a few case studies presented at the first 140 Characters Conference in New York on July 16 and 17 (the number 140 refers to the limit placed on the number of characters in a Twitter post). A good portion of digital sales for Universal Motown Republic’s release of Asher Roth’s "Asleep in the Bread Aisle" was attributed to a Twitter message the day before the album’s release.

How important was Twitter to digital sales? TechCrunch insists it played “an important role.” But not much evidence exists that Roth’s Twitter messages amounted to more than a somewhat effective reminder to likely purchasers. Yes, in the first week digital sales were greater percentage of total album sales than in later weeks. Usually that happens because of pre-orders and the highly impulsive nature of digital marketing. And just consider the work done by Roth and UMR that got Roth so many followers on Twitter in the first place. A Twitter community is a reflection of the effectiveness of pre-existing campaigns to increase awareness. Unless you’re already a celebrity, acquiring Twitter followers costs money.

The truth is that not every Twitter message creates a brand new sale. As with P2P, the question to be asked is what marginal impact a medium has on sales. Some sales were going to happen in the absence of Twitter just as some album’s sales were going to happen without the use of P2P for sampling and previewing. But separating out the sales purely attributable to Twitter is very difficult. One positive aspect of Twitter is its observable cause-and-effect nature: post on Twitter and then track sales, views, streams or downloads that came as a direct result of that post. The value of frequent Twitter posts that have no specific marketing message is not observable. While there’s value in communicating with fans, no hard number can be placed on that value.

Even if Twitter did not increase total sales, it would have a clear value if it merely replaced more expensive means of communicating with fans. Can it replace more time-consuming emails or blog posts? Is it just as effective as an email campaign? If the answer to either question is yes, Twitter is a great medium for music marketing. If the answers are no, Twitter should only be secondary or complementary to other marketing tools.

A problem is that Twitter is very one-dimensional. With email campaigns, an artist or label knows the open rate, can target specific groups of fans and better tailor a message for recipients. Oh, and emails can have complete sentences and consist of hundreds or characters. Twitter is too brief for many uses and, for better or worse, treats all readers the same.