I enjoy Cool Edit by Syntrillium for the typical simple tasks with
digitized audio.  The advertising touts glossy tricks, but the package
actually has very well-designed filters (needed for altering pitch and
time), as well as an adaptive noise filter which works well for hum and
periodic rumble and doesn't introduce severe phase distortion like a
notch filter does.  The analytical tools (power spectrum display,
amplitude statistics, etc.) are good, too.

The program may be downloaded and evaluated free, but only two features
are available simultaneously.  After I decided to buy it I sent about
$50 and received a code number which "unlocks" the restrictions.  See

    http://www.syntrillium.com/

Robbie Rhodes