You have several options and the most popular choices are-

• None - The original keyless chanter dating back to the 18th century. These play the ‘Traditional’ repertoire. There are 8 tone holes giving a standard nominal G scale.
• 7 Keys - Dating from the early 19th century, these are by far the most popular sets and they allow you to play most of the Northumbrian Pipes Repertoire. The scale of the keyless chanter is extended down by three additional notes and up by two. There are also two mid-scale incidentals allowing you to play tunes in nominal G and D.
• 9 or 11 Keys - These sets increase the repertoire available by giving a flattened seventh and/or other incidentals. It allows playing in the nominal key of A.
• 14 Keys - These allow you to play about 90%+ of the current Northumbrian Smallpipe repertoire.
• 17 Keys - These sets are fully chromatic over two octaves. 

The actual notes available depend on the pitch of the set you have chosen. In the table below you can see the notes available for a traditional/F pitch chanter in the left column cross referenced with the number of keys along the top.