No, you don't have to measure, ask google, ba***rd knows everything
Wikipedia is good too. This what I find on instrument:http://en.wikipedia.org/wiki/Vibraphone#Range
So, they say range F3 - F6.
Using next link gives a frequency:http://en.wikipedia.org/wiki/Piano_key_frequencies
33 f F3 174.614
69 f′′′ F6 1396.91
You don't expect me to write all project for you, do you?
I can only provide general guidance, and this is what I came across (google was helpfull):
1. Solder input mic amplifier, or get from sparkfun;
2. Rough estimation shows me that, it will works on UNO. I didn't count memory requirements for tlc5940 or other IC would be in use for output. To play safe and have a slack, Mega 2560 preferable.
Things to read, and absolutely understanding theory behind it, things to modify in software:
1. (FFT) Resolution required for F3 note is 5 Hz. In color-music this value 70 Hz. To make it x16 times better, steps to be taken:
#define FFT_SIZE 512
#define log2FFT 9
2. (Nyquist theorem) Decrease sampling frequency by factor 2, bring it down from 8.8 to 4.4 kHz.
Read two sample, calculate average, store in input array.
It additionally will improve SNR on 3 dB.
3. (Zero padding). Straight forward approach would increase latency in system, approximately
8 times, up to 28 ms x 8 = 224 ms. To keep it below 100 ms, I'd suggest get better resolution by zero padding, not only extending input data array.
But make you research, there a lot of publication "musical note recognition" or similar.