index.js

var remote = require('remote');
var Tray = remote.require('tray');
var Menu = remote.require('menu');
var path = require('path');

var trayIcon = null;

if (process.platform === 'darwin') {
    trayIcon = new Tray(path.join(__dirname, 'img/tray-iconTemplate.png'));
}
else {
    trayIcon = new Tray(path.join(__dirname, 'img/tray-icon-alt.png'));
}

var trayMenuTemplate = [
    {
        label: 'Sound machine',
        enabled: false
    },
    {
        label: 'Settings',
        click: function () {
            ipc.send('open-settings-window');
        }
    },
    {
        label: 'Quit',
        click: function () {
            ipc.send('close-main-window');
        }
    }
];
var trayMenu = Menu.buildFromTemplate(trayMenuTemplate);
trayIcon.setContextMenu(trayMenu);

You'll need these variables to make it work:

const {ipcMain, ipcRenderer, dialog, session, app, BrowserWindow, remote} = require('electron');
const {Menu, Tray} = require('electron').remote;
const path = require('path');

una is right.