fmit (Free Music Instrument Tuner) is a piece of software for tuning musical
instruments, using Qt as a GUI library, supporting ALSA, JACK, OSS, or
PortAudio for audio input. Features error and volume history, tuning scales
using Scala (.scl) files, microtonal tuning, harmonic ratios, wave shapes, and
more. 

fmit will automatically detect ALSA and if jack-audio-connection-kit, oss or
portaudio support is desired, pass JACK="ON", OSS="ON" or PORTAUDIO="ON" to
the SlackBuild.