Sure. You can do decent granular stuff with an iPad Air 2 using software that costs a few bucks, like iPulsare or iDensity, FLUSS, Borderlands or Quanta.
You can add Audiobus, Keystage, Ape Matrix, AUM, Camelot or similar to create a live-environment and add FX plugins etc. Roland has a few decent older class compliant interfaces that you can get for $20-30.
Recommended reading: SoS on granular synthesis
I would encourage you to play around with granular software first, so you can develop an idea what is does and what you need, things labelled “granular” are vastly different, as you can see from that discussion already.
If you own an iPad, that’s probably the cheapest entry point, see above for some recommendations. If you have M4L, use Granulator, and I think Bitwig’s sampler can also be of use.
iPulsaret and iDensity are also available for Mac at ~ $10, but most other granular soft I am aware of costs a lot more on Mac and PC, (see Crusher-X for example), so it might be too expensive for just getting a feel for it. Quanta also not exactly cheap, but is at least available on Mac as a trial version, that might also be sufficient.
Maybe someone else can recommend some decent free software.
I would beg to differ, especially as @_l’s intended use is "noise and ambient.
Here’s what the Octatrack doesn’t provide:
- the elegant simplicity of the tape device (some people just want to load a few samples and loop them, regardless of tempo and length)
- polyphonic sample playing (Poly device)
- granular processing (Mosaic Device)
- the really excellent and versatile morphing resonator (Ring device)
- dual-band processing of the Deform device (you might be able to do an approximation using several channels on the OT, but even then it’s not the same)
Also I know that a lot of people find the OT intimidating, which is certainly not the case with the S4, it is absolutely straightforward to use, you might need to look up how to set up modulators and how to change the mode of a knob, but that’s it.