It is an algorithmic composition tool to make fractal music. It is now also used frequently as a retuning tool for microtonal composition, and for music therapy in conjunction with Barbara Hero’s Lambdoma keyboard. As a microtuner, it is one of the programs that supports MIDI Tuning Standard sysexes.
The application also contains a polyrhythm metronome, a chord progression player, and an audio pitch tracer which can be used for exact tracing of the pitch of microtonal music and birdsong. Other features include a mouse theremin and a PC keyboard player which can be used to explore alternative keyboard layouts such as the Jankó keyboard, which happens to use the same hexagonal type arrangement of keys as a PC keyboard. Version 3.0 introduces an automated Csound orchestra builder and various other new features.
Many of the tunes of Tune Smithy are constructed using self-similar number sequences. They are based on a seed such as 0 1 0. If you take every nth note in the sequence, where n is the number of notes in the seed, you get the original sequence again. So for instance, with the 0 1 0 seed you get the integer sequence 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 2, 3, 2, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 3, 4, 3, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0,  where every third number, highlighted in bold, gives the original sequence again, 0, 1, 0, 1, 2, 1, ...
Then if you take every n2 note, you get the same sequenced again, and so on. By distributing these to different instruments you get an endless sloth canon as a result.
Tune Smithy is also able to play the "Fibonacci gamelan rhythms" of David Canright 
Bounce Metronome Pro
The polyrhythm metronome task in Tune Smithy was developed into a separate program Bounce Metronome Pro which uses conducting visuals to help the musician keep time while playing polyrhythms and other rhythms.
The Scales Composer, a tool to make microtonal scales, is free.
Also the chord progression player - a tool to play any chord progression you paste into it in standard chord notation such as C, A7, etc., is free when used as a player (exporting the chord progression to midi and advanced functions are shareware).
Tune Smithy (for Windows) is one of the programs used by microtonal composers for software midi retuning. The other main ones are Scala, alt-tuner, L'il Miss Scale Oven (for Mac), and Relayer. There are other less frequently used ones as well (see Microtuner.)
- Review of the fractal tunes is the main focus of the Sound on Sound article
- References to Tune Smithy in Tuning, timbre, spectrum, scale By William A. Sethares
- Tune Smithy Software for Lambdoma Keyboard
- The On-Line Encyclopedia of Integer Sequences Number of 1's in ternary (base 3) expansion of n.
- David Canright Fibonacci Gamelan Rhythms
- Short Review of Bounce Metronome in Sound On Sound Magazine - requires subscription to read the original of it
- Scales Composer