Q: what midi interface would work with my iBook g4?

There had been a perhaps-discontinued product known as the iMic or another (different one)

that also uses USB ports in the older PowerPC Mac computer series. These were adapter

kinds of products that allowed other inputs into the computer that otherwise won't work.

Still, I see a listing at the iMic maker web site:

https://store.griffintechnology.com/imic

•Griffin iMic Support information:

http://griffintechnology.com/support/imic

High quality microphones and other audio gear was then able to be used.

A search online may yield something along that line, in a secondhand market.

Or the maker of the original may still offer them, if suitable for your purpose.

Other than that, vintage MIDI equipment may be found in a similar manner.

I cannot suggest anything, as I've not used it with my vintage G3 or G4 Macs.

Good luck & happy computing!

The midi interface works, but only with items with those kind of ports.

The one you posted a link to seems to need Serial ports. Not available

on newer Mac, perhaps on some older Tower G3/G4 or PCI card update.

https://www.google.com/?gws_rd=ssl#q=Mini+Macman+Midiman

While the iMic product allows other product to attach to the audio

circuitry inside the Mac, by use of USB ports. Midi porting isn't native.

So other adapter &/or components would be necessary with midi.

A search of various kinds and models of MIDI (if you even need it?)

would yield several kinds of technologies and some outdated even

more so than the USB2.0 or 1.1 ports on an early iBook G4.

(Some suggest using adapters and network ports, LAN, etc, if you

were set up to choose Ethernet hardware as a path. iMic is easier.)

The item you posted link to has no USB and no way to connect to

the Mac, as you cannot use standard high quality audio equipment

with the iBook G4 without accessing the USB ports. With an iMic

you could also access output, for better quality, or pro headphones.

Some products currently available may not work with the older vintage

iBook G4 hardware, but the iMic can be used to adapt microphones,

and better quality audio equipment to the Mac.

I see one could order the iMic product from the maker web page, but

did not try their site far enough to see if it would take actual orders.

In some locations, you may be able to find a quality second hand one

for less than the asking price (without warranty, though) of a new one.

What kinds of audio are you attempting? Do you have midi hardware

already? The item you posted a link to has no way to connect directly.

But the iMic product from Griffin does connect to a USB port. Easily.

Anyway, more info is needed...

Did you read the iMic -Griffin info?