: Update this section like the others
Here you'll find information on the crystals and oscillators used in various MBHP projects.
You'll also find information on what you can do if you can't find the right crystal or oscillator.
But First, we answer the simple question.
Crystals with parallel cut are optimized for parallel resonance with the oscillator. If you use a crystal with serial cut (which can mostly be found in radio modules), the PIC won't run with the correct frequency. For the PIC to run correctly at 40 MHz, a 10 MHz crystal is required, otherwise the MIDI baudrate will be wrong. Unfortunately every distributor has its own way of identifying the crystal type. If the crystal type is not specified, it's most likely a parallel cut crystal.
There is a forum thread pertaining to crystals which worked with MIDIbox projects:
If your crystal has the correct frequency marked on the casing, but the incorrect number of legs, this can be remedied using a Pierce Oscillator.
Often, if an FM soundcard has a 2-pin oscillator, the neccessary parts to form a pierce oscillator will be found nearby.
In some cases, you can hack this oscillator circuit right off the soundcard with a hacksaw!