My DS5 really enjoyed a keyboard around 6-12 months. Very inexpensive, made for older kids sort of as a toy, but a real keyboard with at least a couple octaves (not the kind with only 5 keys or that lights up when the keys are touched). I noticed that on our real piano he could not make the keys make sounds consistently (often pressed the keys too slowly or without enough force), but an electronic keyboard worked easier.
Read somewhere accounts of the childhoods of musical virtuoso types, some reported that as a young child they recalled music was silly fun in their family, time spent together messing around. The endless hours of practice came later and the drive they had for it and their deep love for making music came to some degree from the memories of the earlier family oriented fun.
The other thing my son enjoyed from early on (can't remember exactly when) was a slide whistle. But they are hit or miss, some of the cheapo kids toys ones kind of just squeak: let me know anyone if you know of where to buy a cheap but reasonable quality one.
Also harmonica and xylophone.
DS did a Music Together type thing but wasn't too keen on the patient sitting in a circle waiting for a turn... the style of the class is likely very dependent on the particular teacher though. He did very much enjoy at 10 months our local library's toddler song time.
