Music
A few examples of what you can ask Wolfram|Alpha about:
get information about a music act
compare music acts
find music acts meeting given criteria
get information about a music album
request specific information about an album
compare albums
get information about a song
request specific information about a song
compute the frequency and other properties of a musical note
specify the octave
calculate the note corresponding to a given frequency
identify several intervals
get information about a chord
specify a chord using lead sheet notation
get information about a key signature
get specific information about a key
get information about a scale
generate sound with a specified waveform
superimpose multiple waveforms
get information about an instrument
find properties of an instrument