Let's be frank for just a moment - when it comes to electronic music, the Roland TB 303 is a sought after sound, the same way the classic Fenders is cherished in Rock n' Roll, the same way the Hammond B3 immediately says "blues and jazz," and the same way the Stradivarius is revered as the gold-standard for baroque violin.
In the electronic music world, though; we're lucky. The fact that the instruments began in electronics and continue in the digital world means there is an immediate translation. Sure, Kontakt may attempt to recreate the best strings in Europe, Garritan may "claim" that they have a "Goffriller" cello library that rivals the real thing - but the truth is the digital recreations pale in comparison with the real thing. And again, just because we're being honest here, it's only due to the fact that people have forgetten what acoustic instruments sound like that these libraries are remotely passable.
But, as was mentioned above; electronic music creators are lucky. Thankfully an awesome 303 sound may be lovingly enjoyed being recreated through the (very affordable $.99 download) emulator "Acid Machine" by Errozero, which was according to the developer, something of a hobby-project. The rack is set up to look much like the classic Propellerhead "Rebirth RB 338" software so popular in the 1990's.
The interface is true to the (now vintage) RB 338 program, And users of the afformentioned UI will find it very easy and enjoyable in terms of workflow. It should be noted, however; that it's not perfect software. It would be nice to have greater control over the drum parts and the portamento of the 303 sounds could use some adjusting. However; for the price tag I don't think we're allowed to complain that much. I see this as a completely viable live performance option and I hope there are DJ's and Producers around who share my vision.
Perhaps the greatest strength with regards to "Acid Machine" is that it is now available in an offline Google-Chrome app form which makes it very much a legitimate music making software. In short, I believe we owe a great debt of gratitude towards Errozero for this remarkable and fun creation.