Before CDs, demos were commonly sent in the form of cassette tapes. Now, "demo tapes" take the form of cassettes, CDs and even MP3 files. CDs are the most popular format and provide high sound quality, but it can take time and money to reproduce them for mass submission. MP3s are becoming more commonplace, as more people have gained high-speed connections. When emailing MP3s, send the audio file as an attachment and include your cover letter and a link to your website.
Ideally, you should include three songs, each less than five minutes. This will give listeners an idea of your music without overwhelming them. The first song on the demo should be the one you consider the best and most accessible. You should also start with your most up-tempo song, as this will help draw in the listener. If you do include a CD with more than three songs, put your best songs first. When submitting a cassette, make sure it's properly cued to play.
Your demo is not complete without a quality CD cover, jacket and label. You can create and print these yourself with the aid of computer software and a color printer. If you need more than just a few, you could also consider printing your materials at a copy center. For even bigger jobs, or for a more professional touch, you can have covers printed by companies who specialize in CD printing, such as recording studios.
When sending your demo, submit neatly typed lyric sheets with it. Include a notice of copyright on the bottom of each sheet and the label of your tape or CD. Include a short, straightforward cover letter that's addressed to a specific person. State the purpose of your demo submission and list any relevant professional credits. Ask for feedback and thank the reader for his time. Include your contact information on all materials. Mail your package in a secure, bubble-lined envelope and include proper postage.